Correlations between photosynthetic enzymes,CO2-fixation and plastid structure in an albino mutant of Zea mays L.

Summary An albino seedling of Zea mays L. was investigated for its potential for CO₂-assimilation. In the mesophyll the number, dimensions and fine structure of chloroplasts are drastically reduced but to a lesser extent in the bundle sheath. Chlorophyll concentration is zero and carotenoid concentration almost zero. Albinism also exerts a strong influence on the stroma of bundle sheath chloroplasts; ribulose-1.5-biphosphate carboxylase (EC 4.1.1.39) activity and glyceraldehyde-3-phosphate dehydrogenase (NADP) (EC 1.2.1.13) activity is not detectable. The C₄-enzymes phosphoenolpyruvate carboxylase (EC 4.1.1.31) and malate dehydrogenase (decarboxylating) (EC 1.1.1.40) and the non-photosynthetic linked enzymes malate dehydrogenase (NAD) (EC 1.1.1.37), aspartate-2-oxoglutarate aminotransferase (EC 1.1.1.37), aspartate-2-oxoglutarate aminotransferase (EC 2.6.1.1.) and glyceraldehyde-3-phosphate dehydrogenase (NAD) (EC 1.2.1.1.) are present in the albino seedling with activities comparable to those in etiolated maize seedlings. The potential for CO₂ fixation of the albino seedlings exceeds that of comparable dark seedlings considerably. The results are discussed with regard to enzyme localization of the C₄ pathway of photosynthesis.Abbreviations Aspartate aminotransferase L-aspartate-2-oxoglutarate aminotransferase-EC 2.6.1.1. - GAPDH (NAD) glyceraldehyde-3-phosphate dehydrogenase (NAD dep.)-EC 1.2.1.12 - GAPDH (NADP) glyceraldehyde-3-phosphate dehydrogenase (NADP dep.)-EC 1.2.1.13 - malic enzyme malate dehydrogenase (NADP dep., decarboxylating)-EC 1.1.1.40 - MDH malate dehydrogenase (NAD dep.)-1.1.1.37 - PEP carboxylase phosphoenolpyruvate carboxylase-EC 4.1.1.31 - RuDP carboxylase ribulose-1.5-biphosphate carboxylase-EC 4.1.1.39     

Activity of enzymes of carbon metabolism during the induction of Crassulacean acid metabolism in Mesembryanthemum crystallinum L.

The maximum extractable activities of twenty-one photosynthetic and glycolytic enzymes were measured in mature leaves of Mesembryanthemum crystallinum plants, grown under a 12 h light 12 h dark photoperiod, exhibiting photosynthetic characteristics of either a C₃ or a Crassulacean acid metabolism (CAM) plant. Following the change from C₃ photosynthesis to CAM in response to an increase in the salinity of in the rooting medium from 100 mM to 400 mM NaCl, the activity of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) increased about 45-fold and the activities of NADP malic enzyme (EC 1.1.1.40) and NAD malic enzyme (EC 1.1.1.38) increased about 4- to 10-fold. Pyruvate, Pi dikinase (EC 2.7.9.1) was not detected in the non-CAM tissue but was present in the CAM tissue; PEP carboxykinase (EC 4.1.1.32) was detected in neither tissue. The induction of CAM was also accompanied by large increases in the activities of the glycolytic enzymes enolase (EC 4.2.1.11), phosphoglyceromutase (EC 2.7.5.3), phosphoglycerate kinase (EC 2.7.2.3), NAD glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12), and glucosephosphate isomerase (EC 2.6.1.2). There were 1.5- to 2-fold increases in the activities of NAD malate dehydrogenase (EC 1.1.1.37), alanine and aspartate aminotransferases (EC 2.6.1.2 and 2.6.1.1 respectively) and NADP glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13). The activities of ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39), fructose-1,6-bisphosphatase (EC 3.1.3.11), phosphofructokinase (EC 2.7.1.11), hexokinase (EC 2.7.1.2) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) remained relatively constant. NADP malate dehydrogenase (EC 1.1.1.82) activity exhibited two pH optima in the non-CAM tissue, one at pH 6.0 and a second at pH 8.0. The activity at pH 8.0 increased as CAM was induced. With the exceptions of hexokinase and glucose-6-phosphate dehydrogenase, the activities of all enzymes examined in extracts from M. crystallinum exhibiting CAM were equal to, or greater than, those required to sustain the maximum rates of carbon flow during acidification and deacidification observed in vivo. There was no day-night variation in the maximum extractable activities of phosphoenolpyruvate carboxylase, NADP malic enzyme, NAD malic enzyme, fructose-1,6-bisphosphatase and NADP malate dehydrogenase in leaves of M. crystallinum undergoing CAM.Abbreviations CAM Crassulacean acid metabolism - PEP phosphoenolpyruvate - RuBP ribulose-1,5-bisphosphate     

Changes in enzyme pattern of Ehrlich ascites tumor cells following serial cultivation in media with increased (hypertonic) NaCl content.

Adaptation of Ehrlich ascites tumor cells to serial cultivation in media with progressively elevated (hypertonic) NaCl content ("high NaCl"-tolerant cells) has resulted in progressive increases of the cellular activities of NAD-dependent glycerol-3-phosphate dehydrogenase (EC 1.1.1.8), NAD-dependent malate dehydrogenase (EC 1.1.1.37), glutamate--oxalacetate transaminase (EC 2.6.1.1), NAD (P)-dependent glutamate dehydrogenase (EC 1.4.1.3), NADP-dependent isocitrate dehydrogenase (EC 1.1.1.42). The activities of glutamate-pyruvate transaminase (EC 2.6.1.2.) and of glycolytic enzymes as phospho-fructokinase (EC 2.7.1.11), glyceraldehydephosphate dehydrogenase (EC 1.2.1.12) and lactate dehydrogenase (EC 1.1.1.27) were only slightly and not in progressive manner (in response to the progressive increase of the environmental NaCl concentration) affected. These changes are discussed with respect to a metabolic pattern of these "high NaCl"-tolerant cells which is compatible with increased energy requirements, especially for active cation transport. It is suggested that these increased cellular enzyme activities reflect an increased transfer of reducing equivalents across mitochondrial membranes (via the "glycerophosphate cycle and the malate-aspartate shuttle") and possibly a stimulated lipid metabolism. These alterations in the level of enzyme activities must be regarded asan adaptive cellular response to the "high NaCl" environment, since readaptation to growth in regular isotonic media resulted in a reversion to the enzyme pattern characteristic of the parent cells.     

Photosynthetic carbon metabolism during leaf ontogeny in Zea mays L.: Enzyme studies

The activities of several enzymes, including ribulose-1,5-diphosphate (RuDP) carboxylase (EC 4.1.1.39) and phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) were measured as a function of leaf age in Z. mays. Mature leaf tissue had a RuDP-carboxylase activity of 296.7 mol CO₂ g^-1 fresh weight h^-1 and a PEP-carboxylase activity of 660.6 mol CO₂ g^-1 fresh weight h^-1. In young corn leaves the activity of the two enzymes was 11 and 29%, respectively, of the mature leaves. In senescent leaf tissue, RuDP carboxylase activity declined more rapidly than that of any of the other enzymes assayed. On a relative basis the activities of NADP malic enzyme (EC 1.1.1.40), aspartate (EC 2.6.1.1) and alanine aminotransferase (EC 2.6.1.2), and NAD malate dehydrogenase (EC 1.1.1.37) exceeded those of both PEP and RuDP carboxylase in young and senescent leaf tissue. Pulse-chase labeling experiments with mature and senescent leaf tissue show that the predominant C₄ acid differs between the two leaf ages. Labeling of alanine in senescent tissue never exceeded 4% of the total ¹⁴C remaining during the chase period, while in mature leaf tissue alanine accounted for 20% of the total after 60 s in ¹²CO₂. The activity of RuDP carboxylase during leaf ontogeny in Z. mays parallels the development of the activity of this enzyme in C₃ plants.Abbreviations RuDP ribulose-1,5-diphosphate - PEP phosphoenol pyruvate - PGA 3-phosphoglycerate     

Investigations of the anaerobic metabolism of the polychaete wormNereis diversicolor M.

Summary The anaerobic metabolism ofNereis diversicolor M. was studied during various periods of experimental anaerobiosis.The degradation of glycogen is shown to be the main source of anaerobic energy production. During first hours of anaerobiosis, aspartate, in addition to glycogen, is metabolized in considerable quantities.Five acids were found to accumulate as end-products: alanine, D-lactate, succinate, acetate and propionate (Table 2).Alanine is accumulated only during the first hours of anaerobiosis. The increase in alanine is correlated with a decrease in aspartate.D-Lactate is the main end-product during the first 24 h of anaerobiosis, and continues to be produced even during prolonged anaerobiosis. In accordance with lactate production,Nereis diversicolor possesses a high glycolytic capacity (Table 4).The major end-products of long term fermentation are propionate and acetate. In contrast to other end-products, these acids are excreted in substantial amounts.Abbreviations GAPDH glyceraldehydephosphate dehydrogenase, EC 1.2.1.12 - LDH lactate dehydrogenase, EC 1.1.1.27 - GOT aspartate aminotransferase, EC 2.6.1.1 - GPT alanine aminotransferase, EC 2.6.1.2 - MDH malate dehydrogenase, EC 1.1.1.37 Supported by Deutsche Forschungsgemeinschaft (Gr 456/5 and Gr 456/6)     

Activity of Carbon Metabolism Enzymes in Wheat Plants Treated with Kartolin-4 and Exposed to Water Stress

Enzymatic activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (EC 4.1.1.39), phospho(enol)pyruvate carboxylase (EC 4.1.1.31), NAD malate dehydrogenase (EC 1.1.1.37), and NADP glyceraldehyde phosphate dehydrogenase complex including phosphoglycerate kinase (EC 2.7.2.3) and glyceraldehyde phosphate dehydrogenase (EC 1.2.1.13) were comparatively assayed in wheat seedlings of the cultivar Lyutestsens 758 grown under normal conditions, water deficiency conditions, and subsequent rehydration. Water stress was found to decrease the activity of all enzymes tested, the effect being most pronounced in the case of Rubisco. The content of Rubisco in wheat plants exposed to water deficiency was reduced less significantly than the activity of the enzyme. Pretreatment of plant seeds with kartolin-4 (o-isopropyl-N-2-hydroxyethyl carbamate), a preparation with cytokinin activity, reduced the dehydration-induced inhibition of enzymatic activity. Upon a subsequent rehydration, kartolin-4 facilitated rapid recovery of the photosynthetic activity, the process being based on the kartolin-induced stimulation of reparation reactions. Under conditions of water stress, a partial decrease in the activity of carbon metabolism enzymes in vitrowas accompanied by complete inhibition of photosynthesis in vivo, perhaps, as a result of an abrupt increase in the stomatal resistance.     

Changes in enzyme pattern of ehrlich ascites tumor cells following serial cultivation in media with increased (hypertonic) NaCl content

Adaptation of Ehrlich ascites tumor cells to serial cultivation in media with progressively elevated (hypertonic) NaCl content (“high NaCl”-tolerant cells) has resulted in progressive increases of the cellular activities of NAD-dependent glycerol-3-phosohate dehydrogenase (EC 1.1.1.8), NAD-dependent malate dehydrogenase (EC 1.1.1.37), glutamate—oxalacetate transaminase (EC 2.6.1.1.), NAD(P)-dependent glutamate dehydrogenase (EC 1.4.1.3), NADP-dependent malate dehydrogenase (EC 1.1.1.40, “malic enzyme”) and NADP-dependent isocitrate dehydrogenase (EC 1.1.1.42). The activities of glutamate—pyruvate transaminase (EC 2.6.1.2.) and of glycolytic enzymes as phosphofructokinase (EC 2.7.1.11), glyceradehydephosphate dehydrogenase (EC 1.2.1.12) and lactate dehydrogenase (EC 1.1.1.27) were only slightly and not in progressive manner (in response to the progressive increase of the environmental NaCl concentration) affected. These changes are discussed with respect to a metabolic pattern of these “high NaCl”-tolerant cells which is compatible with increased energy requirements, especially for active cation transport. It is suggested that these increased cellular enzyme activitees reflect an increased transfer of reducing equivalents across mitochondrial membranes (via the “glycerophosphate cycle and the malate—aspartate shuttle”) and possibly a stimulated lipid metabolism. These alterations in the level of enzyme activities must be regarded as an adaptive cellular response to the “high NaCl” enviromment, since readaptation to growth in regular isotonic media resulted in a reversion to the enzyme pattern characteristic of the parent cells.     

Activity of carbon metabolism enzymes in wheat plants treated with kartolin-4 and exposed to water stress]

Enzymatic activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (EC 4.1.1.39), phospho(enol)pyruvate carboxylase (EC 4.1.1.31), NAD malate dehydrogenase (EC 1.1.1.37), and NADP glyceraldehydephosphate dehydrogenase complex including phosphoglycerate kinase (EC 2.7.2.3) and glyceraldehydephosphate dehydrogenase (EC 1.2.1.13) were comparatively assayed in wheat seedlings of the cultivar Lyutestsens 758 grown under normal conditions, water deficiency conditions, and subsequent rehydration. Water stress was found to decrease the activity of all enzymes tested, the effect being most pronounced in case of Rubisco. The content of Rubisco in wheat plants exposed to water deficiency was reduced less significantly than the activity of the enzyme. Preliminary treatment of plant seeds with kartolin-4 (o-isopropyl-N-2-hydroxyethyl carbamate), a preparation with cytokinin activity, reduced the dehydration-induced inhibition of enzymatic activity. Upon a subsequent rehydration, kartolin-4 facilitated rapid recovery of the photosynthetic activity, the process being based on the kartolin-induced stimulation of reparation reactions. Under conditions of water stress, a partial decrease in the activity of carbon metabolism enzymes in vitro was accompanied by complete inhibition of photosynthesis in vivo, perhaps, as a result of an abrupt increase in the stomatal resistance.     

Transaminase reactions and glutamate dehydrogenase in gastropod hepatopancreas

Summary Hepatopancreas tissue from the terrestrial snailsOtala lactea, Helix aspersa andStrophocheilus oblongus and the aquatic snailsBiomphalaria glabrata, Viviparus viviparus andLymnaea stagnalis was investigated for the presence of the various transaminases and glutamate dehydrogenase (EC 1.4.1.2 L-glutamate: NAD⁺ oxidoreductase). The cytosolic transaminases showed a broad substrate specificity, transferring the -amino function of most amino acids to -ketoglutarate. The main transaminase activities present were those of asparate transaminase (EC 2.6.1.1 L-aspartate: 2-oxoglutarate aminotransferase) and alanine transaminase (EC 2.6.1.2 L-alanine: 2-oxoglutarate aminotransferase). These two transaminases were also present in the mitochondrial fraction and thus exist in gastropod hepatopancreas as isozymes.Low levels of glutamate dehydrogenase activity were detected in hepatopancreas mitochondria from terrestrial and aquatic snails. The activity appears to be that of a typical animal glutamate dehydrogenase, preferentially utilizing NAD⁺ as a cofactor and being activated by adenine nucleotides and inhibited by guanine nucleotides.Supported by grants from the USPHS (AI 05006 and DE-00118) and the NSF (GB-38138)     

Some enzyme activities associated with the chlorophyll containing layers of the immature barley pericarp

Summary Some photosynthetic and biochemical properties of the chlorophyl containing layers of the pericarp of developing barley have been investigated. The tissue changes from pale green to bright green early in development, chlorophyll disappearing only at the later stages of maturity. It contains chloroplasts and probably amyloplasts and starch bearing chloroplasts. It is capable of high rates of light dependent oxygen evolution. It has been shown that the enzyme phosphoenol pyruvate carboxylase (EC 4.1.1.31) is present in the pericarp and is 100 times as active in carbon dioxide fixation as ribulose diphosphate carboxylase (EC 4.1.1.39). Other enzymes present in the pericarp are phosphoenol pyruvate synthetase, pyrophosphatase (EC 3.6.1.1), malate NAD and NADP dehydrogenases (EC 1.1.1.37), malic enzyme (EC 1.1.1.40), and fructose 1,6 diphosphatase (EC 3.1.3.11).Abbreviations RDP Ribulose 1,5-diphosphate - PEP phosphoenol pyruvate     

Products of photosynthetic 14CO2 fixation and related enzyme activities in fruiting structures of chickpea

Fruiting structures of a number of legumes including chickpea are known to carry out photosynthetic CO₂ assimilation, but the pathway of CO₂ fixation and particularly the role of phosphoenolpyruvate carboxylase (EC 4.1.1.31) in these tissues is not clear. Activities of some key enzymes of the Calvin cycle and C₄ metabolism, rates of ¹⁴CO₂ fixation in light and dark, and initial products of photosynthetic ¹⁴CO₂ fixation were determined in podwall and seedcoat (fruiting structures) and their subtending leaf in chickpea (Cicer arietinum L.). Compared to activities of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and other Calvin cycle enzyme, viz. NADP⁺-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13), NAD⁺-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) and ribulose-5-phosphate kinase (EC 2.7.1.19), the levels of phosphoenolpyruvate carboxylase and other enzymes of C₄ metabolism viz. NADP⁺-malate dehydrogenase (EC 1.1.1.82), NAD⁺-malate dehydrogenase (EC 1.1.1.37), NADP⁺ malic enzyme (EC 1.1.1.40), NAD⁺-malic enzyme (EC 1.1.1.39), glutamate oxaloacetate transaminase (EC 2.6.1.1) and glutamate pyruvate transaminase (EC 2.6.1.2), were generally much higher in podwall and seedcoat than in the leaf. Podwall and seedcoat fixed ¹⁴CO₂ in light and dark at much higher rates than the leaf. Short-term assimilation of ¹⁴CO₂ by illuminated fruiting structures produced malate as the major labelled product with less labelling in 3-phosphoglycerate, whereas the leaf showed a major incorporation into 3-phosphoglycerate. It seems likely that the fruiting structures of chickpea utilize phosphoenolpyruvate carboxylase for recapturing the respired carbon dioxide.     

A new glutamate dehydrogenase from Halobacterium halobium with different coenzyme specificity

• 1.1. Halobacterium halobium has two chromatographically distinct forms of glutamate dehydrogenase which differ in their thermolability and other properties. One glutamate dehydrogenase utilizes NAD, the other NADP as a coenzyme.
• 2.2. The NADP-specific glutamate dehydrogenase (EC 1.4.1.4) was purified 65-fold from crude extracts of H. halobium.
• 3.3. The Michaelis constants for 2-oxoglutarate (13.3 mM), ammonium (3.1 mM) and NADPH (0.077 mM) indicate that the enzyme catalyzes in vivo the formation of glutamate from ammonium and 2-oxoglutarate.
• 4.4. The amination of 2-oxoglutarate by NADP-specific glutamate dehydrogenase is optimal at the pH value of 8.0–8.5. The optimal NaCl or KCl concentration for the reaction is 1.6 M.
• 5.5. None of the several metabolites tested for a possible role in the regulation of glutamate dehydrogenase activity appeared to exert an appreciable influence on the enzyme.
• 6.6. NAD- and NADP-dependent glutamate dehydrogenases from H. halobium showed apparent molecular weights of 148,000 and 215,000 respectively.

     

Acetyl coenzyme A and coenzyme A contents of growing Clostridium kluyveri as determined by isotope assays

CoASH and some of its acyl derivatives, especially acetyl-SCoA, occupy a central position in the energy metabolism of the anaerobic Clostridium kluyveri, both as intermediates and as regulatory effectors. The steady state concentrations of these compounds were determined in growing cultures of this organism using an anaerobic and fast deproteinization technique and radio isotope assays. Acetyl-SCoA was determined as [1-¹⁴C]citrate formed in the presence of [4-¹⁴C]oxaloacetate and citrate synthase; 0.49 mol/g cell wet wt. were found CoASH, CoAS-SCoA after borohydride reduction, and total acyl derivatives of coenzyme A after hydrolysis of the thiol esters were converted to thioethers with [2,3-¹⁴C]N-ethylmaleimide and brought to radiochemical purity by chromatographic methods. While disulfides of coenzyme A were undetectable, 0.13 mol CoASH and 1.17 mol of total acyl-SCoA per g wet wt. were found. These data are consistent with the regulatory scheme of the energy metabolism of C. kluyveri previously proposed.Abbreviations DTE dithioerythritol - NEM N-ethylmaleimide - NES N-ethylsuccinimide Enzymes (EC 2.7.2.1) Acetate kinase, ATP: acetate phosphotransferase - (EC 3.1.3.1) Alkaline phosphatase, orthophosphoric monoester phosphohydrolase - (GOT) Aspartate aminotransferase - (EC 2.6.1.1) L-aspartate:2-oxoglutarate aminotransferase - (CS) Citrate synthase - (EC 4.1.3.7) citrate oxaloacetate-lyase (pro 3S-CH₂COOacetyl-CoA) - (EC 2.8.3.8) CoA-transferase, acyl-CoA:acetate CoA-transferase - (EC 1.1.1.37) Malate dehydrogenase, L-malate:NAD⁺ oxidoreductase - (EC 1.18.1.3) NADH:ferredoxin reductase, ferredoxin:NAD⁺ oxidoreductase - (EC 3.1.4.1) Phosphodiesterase (snake venom), orthophosphoric diester phosphohydrolase - (EC 2.3.1.8) Phosphotransacetylase, acetyl-CoA:orthophosphate acetyltransferase - (EC 2.3.1.9) Thiolase, acetyl-CoA:acetyl-CoA C-acetyltransferase A preliminary account of this work has been given (Decker et al. 1976)     

Carboxylating enzymes and pathway of photosynthetic carbon assmilation in different marine algae—Evidence for the C4-pathway?

Experiments on short-term photosynthesis in H¹⁴CO₃ ^- (2–5 s) using various species of different algal classes resulted in predominant ¹⁴C-labelling (>90% of total ¹⁴C-incorporation) of phosphorylated compounds. The percentage of malate and aspartate usually accounts for distinctly less than 10% of the total ¹⁴C-labelling. These findings are consistent with data from enzymatic analyses, since 97–100% of the carboxylation capacity is due to ribulose-1.5-biphosphate carboxylase (EC 4.1.1.39) in Rhodophyceae and Chlorophyceae. Phaeophyceae are generally characterized by considerable activity of phosphoenolpyruvate carboxykinase (EC 4.1.1.32): at least 10% of carboxylation is confined to this enzyme. Similar ratios are obtained when rates of photosynthesis and of light-independent CO₂-fixation are compared. Activity of phosphoenolpyruvate carboxylase (EC 4.1.1.31) could not be detected in the species investigated. The results are discussed with emphasis on the pathway of photosynthetic carbon assimilation in marine algae.Abbreviations PEP-CK phosphoenolpyruvate carboxykinase (EC 4.1.1.32) - PEP-C phosphoenolpyruvate carboxylase (EC 4.1.1.31) - RubP-C ribulose-1.5-biphosphate carboxylase (EC 4.1.1.39) Dedicated to Professor H. Fischer, Bonn, on his 65th birthday     

Schistosoma haematobium: oxidoreductase histochemistry and ultrastructure of niridazole-treated females

Administration of niridazole to Saccostomus campestris produced changes in enzyme activity in Schislosoma haematobium females as indicated histochemically by a decrease in the activity of cytochrome oxidase (EC 1.9.3.1), malate (NAD) dehydrogenase (EC 1.1.1.37), malate (NADP) dehydrogenase (EC 1.1.1.40), succinate dehydrogenase (EC 1.3.99.11), isocitrate (NAD) dehydrogenase (EC 1.1.1.41), isocitrate (NADP) dehydrogenase (EC 1.1.1.42), lactate dehydrogenase (EC 1.1.1.27), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), NADH: tetrazolium oxidoreductase, NADPH: tetrazolium oxidoreductase, and a disappearance of both the activity of phenolase (EC 1.10.3.1) and the reactivity of vitelline phenols. These changes were associated with the following alterations in the ultrastructure of the parasites: a decrease in number of immature vitelline cells of gonial type, a disruption of the tegument surface, a swelling of mitochondria in vitelline cells, a disappearance of the regular structure of the endoplasmic reticulum and a vaeuolization of the cytoplasm in vitelline cells, an appearance of areas of focal cytoplasmic degradation in vitelline cells, and a disruption of shell globules. The degree of changes in enzyme activity and ultrastructure increased both with increase in the dose of niridazole administered to the hosts, and with length of time after treatment.Preincubation of control sectioned material in a buffered niridazole-sucrose solution produced total inhibition of succinate dehydrogenase activity, whereas the activity of other enzymes examined remained unchanged.     

Specific action of blue light on phytochrome-mediated enzyme syntheses in the shoot of milo (Sorghum vulgare Pers.)

Abstract. This paper describes the effect of prolonged treatments with red or blue light on the capacity of the milo ( Sorghum vulgare Pers.) shoot to respond to Pfr in subsequent darkness. Two groups of enzymes were studied. In group I (NADP-dependent glyceraldehyde-3-phosphate dehydrogenase, NADP-GPD. EC 1.2.1.13 and ribulose-bisphosphate carboxylase, carboxylase, EC 4.1.1.39) enzyme formation is strongly enhanced by red light pulses (operating through phytochrome) whereas in group II (NAD-dependent glyceraldehyde-3-phosphate dehydrogenase, NAD-GPD, EC 1.2.1.12 and NAD-dependent malate dehydrogenase, MDH. EC 1.1.1.37) enzyme formation hardly responds to red light pulses.
In group 1 a 24-h treatment with blue light (but not with red light) leads to a strong increase in responsivity to Pfr whereas in group II a 24-h treatment with blue or red light does not increase responsivity to Pfr in subsequent darkness.
The specific effect of blue light cannot be explained by an effect of light on gross protein synthesis. Rather, the data indicate that amplification of responsivity to Pfr by blue light is a specific process directly related to the mechanism of modulation of gene expression by phytochrome.     

INHIBITION OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE IN MAMMALIAN NERVE BY IODOACETIC ACID

Abstract— Cat sciatic nerves were exposed to iodoacetate for a period of 5–10 min and after washing out the iodoacetate, the enzymes, glyceraldehyde-3-phosphate dehydrogenase ( d -glyceraldehyde-3-phosphate: NAD oxidoreductase (phosphorylating); EC 1.2.1.12) and lactate dehydrogenase ( l -lactate: NAD oxidoreductase; EC 1.1.1.27) were extracted from the high-speed supernatant fraction of nerve homogenates. Concentrations of iodoacetate as low as 2.5 m m could completely block activity of glyceraldehyde-3-phosphate dehydrogenase but had no effect on lactate dehydrogenase. These findings are in accord with the classical concept shown earlier for muscle that iodoacetate blocks glycolysis by its action on glyceraldehyde-3-phosphate dehydrogenase. A complete block of activity of the enzyme was found after treatment with 2 to 5 m m -iodoacetate for a period of 10 min and such blocks were irreversible for at least 3 h. Glyceraldehyde-3-phosphate dehydrogenase activity was NAD specific, with NADP unable to substitute for NAD. The results are discussed in relation to the effect of iodoacetate in blocking glycolysis and in turn the fast axoplasmic transport of materials in mammalian nerve.     

Enhancement of aldehyde dehydrogenase activity in human and rat hepatocyte cultures by 3-methylcholanthrene

Aldehyde dehydrogenase was measured in primary cultures of hepatocytes obtained with a two-step collagenase perfusion either from human hepatic tissue or from livers of Fisher rats. Basal enzyme activity declines gradually as a function of time in culture, but remains at all times higher when measured with propionaldehyde and NAD (P/NAD) than with benzaldehyde and NADP (B/NADP). Treatment of the cultures with 2 M of 3-methylcholanthrene for four days significantly increased the B-NADP activity of human and rat hepatocytes (tenfold and eightfold respectively). In human hepatocytes 3-methylcholanthrene increases also the P/NAD activity, but to a lesser extent (twofold), compared to the B/NADP activity. Due to the significant enhancement of B/NADP activity in cultures of human and rat hepatocytes after application of 3-methylcholanthrene, the initial difference in the basal activity levels between the P/NAD and B/NADP forms diminishes or, in the case of human hepatocytes, is even inverted. These results show for the first time that aldehyde dehydrogenase activity is increased in cultured human hepatocytes. This biochemical property is preserved in human and rat hepatocyte cultures, despite the rather quick loss of the basal aldehyde dehydrogenase activity.Abbreviations ALDH aldehyde dehydrogenase - B benzaldehyde - p-p-DDT 1,1,1,-trichlo-2,2,bis(p-chlorophenyl)ethane - DMSO dimethylsulfoxide - 3-MC 3-methylcholanthrene - MEM Minimal Essential Medium - P proprionaldehyde - TCDD 2,3,7,8-tetrachlorodibenzo-p-dioxin     

Profile of Basic Carbon Pathways in Guard Cells and Other Leaf Cells of Vicia faba L

Guard cells and three other cell types from Vicia faba L. `Longpod' leaflets were assayed for enzymes that catalyze one step in each of five major carbon pathways in green plants: the photosynthetic carbon reduction pathway (ribulose-bisphosphate carboxylase, EC 4.1.1.39), the photosynthetic carbon oxidation pathway (hydroxypyruvate reductase, EC 1.1.1.81), glycolysis ([NAD] glyceraldehyde-P dehydrogenase, EC 1.2.1.12), the oxidative pentose-P pathway (6-P-gluconate dehydrogenase, EC 1.1.1.44), and the tricarboxylic acid pathway (fumarase, EC 4.2.1.2). Neither ribulose-bisphosphate carboxylase nor hydroxypyruvate reductase could be detected in guard cells or epidermal cells; high levels of these activities were present in mesophyll cells. The specific activity of fumarase (protein basis) was about 4-fold higher in guard cells than in epidermal, palisade parenchyma or spongy parenchyma cells. (NAD) glyceraldehyde-P and 6-P-gluconate dehydrogenases also were present at high protein specific activities in guard cells (2- to 4-fold that in meosphyll cells).

It was concluded that the capacity for metabolite flux through the catabolic pathways is high in guard cells. In addition, other support is provided for the view that photoreduction of CO₂ by these guard cells is absent.