Enzyme activity profiles in an overwintering population of freeze-tolerant larvae of the gall fly,Eurosta solidaginis

The activity of some enzymes of intermediary metabolism, including enzymes of glycolysis, the hexose monophosphate shunt, and polyol cryoprotectant synthesis, were measured in freeze-tolerant Eurosta solidaginis larvae over a winter season and upon entry into pupation. Flexible metabolic rearrangement was observed concurrently with acclimatization and development. Profiles of enzyme activities related to the metabolism of the cryoprotectant glycerol indicated that fall biosynthesis may occur from two possible pathways: 1. glyceraldehyde-phosphate glyceraldehyde glycerol, using glyceraldehyde phosphatase and NADPH-linked polyol dehydrogenase, or 2. dihydroxyacetonephosphate glycerol-3-phosphate glycerol, using glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase. Clearance of glycerol in the spring appeared to occur by a novel route through the action of polyol dehydrogenase and glyceraldehyde kinase. Profiles of enzyme activities associated with sorbitol metabolism suggested that this polyol cryoprotectant was synthesized from glucose-6-phosphate through the action of glucose-6-phosphatase and NADPH-linked polyol dehydrogenase. Removal of sorbitol in the spring appeared to occur through the action of sorbitol dehydrogenase and hexokinase. Glycogen phosphorylase activation ensured the required flow of carbon into the synthesis of both glycerol and sorbitol. Little change was seen in the activity of glycolytic or hexose monophosphate shunt enzymes over the winter. Increased activity of the -glycerophosphate shuttle in the spring, indicated by greatly increased glycerol-3-phosphate dehydrogenase activity, may be key to removal and oxidation of reducing equivalents generated from polyol cryoprotectan catabolism.Abbreviations 6PGDH 6-Phosphogluconate dehydrogenase - DHAP dihydroxy acetone phosphate - F6P fructose-6-phosphate - F6Pase fructose-6-phospha-tase - FBPase fructose-bisphosphatase - G3P glycerol-3-phosphate - G3Pase glycerol-3-phosphate phophatase - G3PDH glycerol-3-phosphate dehydrogenase - G6P glucose-6-phosphate - G6Pase glucose-6-phosphatase - G6PDH glucose-6-phosphate dehydrogenase - GAK glyceraldehyde kinase - GAP glyceraldehyde-3-phosphate - GAPase glyceraldehyde-3-phosphatase - GAPDH glyceraldehyde-3-phosphate dehydrogenase - GDH glycerol dehydrogenase - GPase glycogen phosphorylase - HMS hexose monophosphate shunt - LDH lactate dehydrogenase - NADP-IDH NADP⁺-dependent isocitrate dehydrogenase - PDHald polyol dehydrogenase, glyceraldehyde activity - PDHgluc polyol dehydrogenase, glucose activity - PFK phosphofructokinase - PGI phosphoglucoisomerase - PGK phosphoglycerate kinase - PGM phosphoglucomutase - PK pyruvate kinase - PMSF phenylmethylsulfonylfluoride - SoDH sorbitol dehydrogenase - V _max maximal enzyme activity - ww wet weight     

Distribution of erythrocytic allozymes in two sibling species of greater galago [Galago crassicaudatus E. Geoffroy 1812 and G. garnettii (Ogilby 1838)]

This study investigated the use of erythrocyte enzymes as indicators of the presence or absence of gene flow between the sibling species G. crassicaudatus and G. garnettii. Fifty-five animals deriving from 14 different source populations were included in the analyses. In addition to hemoglobin, eight enzyme systems were examined: acid phosphatase, adenylate kinase, carbonic anhydrase II, esterase D, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, peptidase A, and peptidase B. of these, adenylate kinase, glucose-6-phosphate dehydrogenase, hemoglobin, peptidase A, and peptidase B showed no interspecific or intraspecific variation. Esterase D was polymorphic in certain populations of G. crassicaudatus but not in others or in G. garnettii. Acid phosphatase and 6-phosphogluconate dehydrogenase were polymorphic in G. garnettii but monomorphic in all G. crassicaudatus populations. The taxa showed fixation for different alleles at the carbonic anhydrase II locus, indicating a lack of gene exchange between the taxa. We suggest that acid phosphatase, 6-phosphogluconate dehydrogenase, and carbonic anhydrase II may be used as genetic markers in the identification of these two taxa.     

Hydrolysis of G6P by a microsomal aspecific phosphatase and glucose phosphorylation by a low K m hexokinase in the digestive gland of the crab Carcinus maenas: variations during the moult cycle

Summary The hydrolysis of glucose-6-phospate in the digestive gland of the crab Carcinus maenas is carried out by an aspecific phosphatase. This enzyme possesses the following features: (1) insensitivity to acid treatment; (2) absence of inhibition when exposed to citrate at low pH; (3) similar affinity for G6P as the acid phosphatase for Na--glycerophosphate (K _m 2.3 and 2.0 mM, respectively). Glucose-6-phosphate and Na--glycerophate hydrolysis reactions seem to be catalysed by the same enzyme, since both activities exhibit the same distribution in a subcellular fractionation of the gland. Furthermore, as these activities are principally recovered in the subcellular fraction enriched in calcospherites (or calcium phosphate granules), it is proposed that the aspecific G6P-phosphohydrolase could play a major role in the formation of these granules. The phosphorylation of glucose is made by two low K _m hexokinases (230 and 64 M, respectively). As their level of activity shows significant changes over the moult cycle, these enzymes could be considered as having a regulatory role in the storage of glucose in the digestive gland.Abbreviations Acid Pase aspecific acid phosphatase - ATP adenosine triphosphate - DTT dithiothreitol - EDTA ethylenediaminetetra-acetate - G calcium phosphate granules fraction - G6P glucose-6-phosphate - G6Pase hepatic glucose-6-phosphatase - G6PDH glucose-6-phosphate dehydrogenase - K _m Michaelis-Menten constant - MI mitochondria and intermediate postmitochondrial particles - N nuclei fraction - NADH nicotineamide adenine dinucleotide - P microsome fraction - Pi inorganic phosphate - PMSF phenylmethylsulphonylfluoride - STI soybean trypsin inhibitor - glyP Na--glycerophosphate - T_1,2,3 transport protein 1,2,3 - TCA trichloroacetic acid     

Pentose phosphate metabolism during dormancy breakage in Corylus avellana L.

Commercially obtained fruits of Corylus avellana exhibit the characteristic loss of dormancy of this seed following chilling under moist conditions. The activities of cytosolic and organellar enzymes of pentose phosphate pathway in cotyledonary tissue were assayed throughout stratification and over a similar period in damp vermiculite at 20° C. Glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconic acid dehydrogenase (6PGDH) were both found in cytosolic extracts in all treatments; only 6PGDH was present in the organellar fraction.The enzyme activities monitored in seeds at 20° C remained relatively constant over the course of the investigation except in the case of cytosolic 6PGDH where it is suggested an inhibitor of the enzyme accumulated. This inhibitor was removed by the partial purification procedure. Increases in the activities of the enzymes occurred during stratification, the major increase coinciding exactly with dormancy breakage but prior to the initiation of germination. The marked increase in G6PDH and 6PGDH concurrent with the change in germination potential of the chilled seed may have considerable biochemical significance in breaking down the dormant state.Abbreviations G6P glucose-6-phosphate - G6PDH glucose-6 phosphate dehydrogenase - NADP nicotinamide adenine dinucleotide phosphate - 6 PGDH 6-phosphogluconic acid dehydrogenase - PPP pentose phosphate pathway     

Red cell isozymes in the Eastern Carolines

Four populations of islanders (Ponapeans, Mokilese, Pingelapese, and Kusaieans) in the Eastern Caroline Islands have been surveyed for variability in red cell acid phosphatase, phosphoglucomutase, 6-phosphogluconate dehydrogenase, adenylate kinase and glucose-6-phosphate dehydrogenase. The following gene frequencies were observed: P^a = 0.0904, PGM²₁ = 0.1015, and PGD^B = 0.0259. No genetic variation was encountered in the AK and G6PD systems.     

The influence of temperature on glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and the regulation of these enzymes in a mesophilic and a thermophilic cyanobacterium

The activities and kinetics of the enzymes G6PDH (glucose-6-phosphate dehydrogenase) and 6PGDH (6-phosphogluconate dehydrogenase) from the mesophilic cyanobacterium Synechococcus 6307 and the thermophilic cyanobacterium Synechococcus 6716 are studied in relation to temperature. In Synechococcus 6307 the apparent K _m's are for G6PDH: 80M (substrate) and 20M (NADP⁺); for 6PGDH: 90M (substrate) and 25M (NADP⁺). In Synechococcus 6716 the apparent K _m's are for G6PDH: 550M (substrate) and 30M (NADP⁺); for 6PGDH: 40M (substrate) and 10M (NADP⁺). None of the K _m's is influenced by the growth temperature and only the K _m's of G6PDH for G6P are influenced by the assay temperature in both organisms. The idea that, in general, thermophilic enzymes possess a lower affinity for their substrates and co-enzymes than mesophilic enzymes is challenged.Although ATP, ribulose-1,5-bisphosphate, NADPH and pH can all influence the activities of G6PDH and 6PGDH to a certain extent (without any difference between the mesophilic and the thermophilic strain), they cannot be responsible for the total deactivation of the enzyme activities observed in the light, thus blocking the pentose phosphate pathway.Abbreviations G6PDH glucose-6-phosphate, dehydrogenase - 6PGDH 6-phosphogluconate dehydrogenase - G6P glucose-6-phosphate - 6PG 6-phosphogluconate - RUDP ribulose-1,5-bisphosphate - Tricine N-Tris (hydroxymethyl)-methylglycine     

Disturbed sugar metabolism in a fully habituated nonorganogenic callus of Beta vulgaris (L.)

Habituated (H) nonorganogenic sugarbeet callus was found to exhibit a disturbed sugar metabolism. In contrast to cells from normal (N) callus, H cells accumulate glucose and fructose and show an abnormal high fructose/glucose ratio. Moreover, H cells which have decreased wall components, display lower glycolytic enzyme activities (hexose phosphate isomerase and phosphofructokinase) which is compensated by higher activities of the enzymes of the hexose monophosphate pathway (glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase). The disturbed sugar metabolism of the H callus is discussed in relation to a deficiency in H₂O₂ detoxifying systems.Abbreviations 6PG-DH 6-phosphogluconate dehydrogenase - G6P-DH glucose-6-phosphate dehydrogenase - H fully habituated callus - HK hexokinase - HMP hexoses monophosphate - HPI hexose phosphate isomerase - N normal callus - PFK phosphofructokinase     

Quantitative enzyme histochemistry of rat foetal brain and trigeminal ganglion

Summary The increasing concern and the efforts in determining neurological effects in offsprings resulting from maternal exposure to xenobiotics are faced with several difficulties in monitoring damage to the central nervous system. In this paper, the efficiency of several enzyme histochemical reactions for analysing the forebrain and the trigeminal ganglia of rat foetuses are reported. Brains of 20-day-old Sprague-Dawley rat foetuses were frozen and analysed for 18 enzymes that had previously been used to monitor initial injury caused by toxic compounds in liver and other organs. Eight enzymes appeared suitable as histochemical markers for the functional integrity of different areas in brain and ganglia of rats exposed to xenobiotics. They were lactate, malate, glycerophosphate (NAD-linked), succinate, aldehyde and glucose 6-phosphate dehydrogenases, -glycerophosphate-menadione oxidoreductase and cytochromec oxidase. The activities of the enzymes were determined by microphotometry and the arrangement of absorbances of the enzyme final reaction products into appropriate analytical tables is proposed as an efficient procedure for data analysis.Abbreviations AcChE acetylcholinesterase - AldDH aldehyde dehydrogenase - ALKPase alkaline phosphatase - 5AMPase adenosine monophosphatase - ATPase Mg²⁺ dependent adenosine triphosphatase - CytOx cytochromec oxidase - GAPDH glyceraldehyde phosphate dehydrogenase - GIDH glutamate dehydrogenase - GLPDH glycerophosphate: NAD oxidoreductase - CPODH glycerophosphate:menadione oxidoreductase - G6Pase glucose-6-phosphatase - G6PDH glucose-6-phosphate dehydrogenase - IDH lactate dehydrogenase - MaDH malate dehydrogenase - MAO monoamine oxidase - NADPH, DH, NADPH tetrazolium oxidoreductase - SuDH succinate dehydrogenase - 6PGDH 6-phosphogluconate dehydrogenase     

Influence of very low doses of ionizing radiation on Synechococcus lividus metabolism during the initial growth phase

Previous results from this laboratory have shown that very low chronic doses of gamma radiation can stimulate proliferation of the Cyanobacterium Synechococcus lividus. This modification of cell proliferation occurred during the first doubling. In this paper, we have compared the metabolism of cells cultivated in a normal environment or under chronic irradiation. Incubation of the cells in a new medium induced a high superoxide dismutase (EC 1.15.1.1, SOD) activity at the 18th hour and a degradation of phycocyanin, thus demonstrating that cells were submitted to a photooxidative stress. This increase in superoxide dismutase activity was followed by concomittant peaks of glutathione reductase (EC 1.6.4.2, GR) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6P-DH) at the 24th hour. Irradiated cultures at a dose of 53.5 mGray/year show an earlier and higher peak of SOD, GR, and G6P-DH. In a second stage, cultures showed an earlier onset of photosynthesis under irradiation, as evidenced by an increase in pigment content and an enhancement of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13, GAP-DH). These results show that the radiostimulation is related to the activation of enzymes protecting against peroxides that were induced under oxidative circumstances and to the activation of a glucose catabolism via the oxidative pentose phosphate pathway.Abbreviations mGy milli-Gray - SOD superoxide dismutase - G6P-DH glucose-6-phosphate dehydrogenase - GAP-DH glycer-aldehyde-3-phosphate dehydrogenase - GSSG oxidized glutathione     

Glucose-6-phosphate dehydrogenase of Anabaena sp.

The kinetic and molecular properties of cyanobacterial glucose-6-phosphate dehydrogenase, partly purified from Anabaena sp. ATCC 27893, show that it undergoes relatively slow, reversible transitions between different aggregation states which differ in catalytic activity. Sucrose gradient centrifugation and polyacrylamide gel electrophoresis reveal three principal forms, with approximate molecular weights of 120 000 (M ₁), 240 000 (M ₂) and 345 000 (M ₃). The relative catalytic activities are: M ₁M ₂<M ₃. In concentrated solutions of the enzyme, the equilibrium favors the more active, oligomeric forms. Dilution in the absence of effectors shifts the equilibrium in favor of the M ₁ form, with a marked diminution of catalytic activity. This transition is prevented by a substrate, glucose-6-phosphate, and also by glutamine. The other substrate, nicotinamide adenine dinucleotide phosphate (NADP⁺), and (in crude cell-free extracts) ribulose-1,5-diphosphate are negative effectors, which tend to maintain the enzyme in the M ₁ form. The equilibrium state between different forms of the enzyme is also strongly dependent on hydrogen ion concentration. Although the optimal pH for catalytic activity is 7.4, dissociation to the hypoactive M ₁ form is favored at pH values above 7; a pH of 6.5 is optimal for maintenace of the enzyme in the active state. Reduced nicotamide adenine dinucleotide phosphate (NADPH) and adenosine 5-triphosphate (ATP), inhibit catalytic activity, but do not significantly affect the equilibrium state. The relevance of these findings to the regulation of enzyme activity in vivo is discussed.Abbreviations G6PD glucose-6-phosphate dehydrogenase - 6PGD 6-phosphogluconate dehydrogenase - RUDP ribulose-1,5-diphosphate - G6P glucose-6-phosphate - 6PG 6-phosphogluconate     

Cloning and sequence analysis of the glucose-6-phosphate dehydrogenase gene from the cyanobacterium Synechococcus PCC 7942

The glucose-6-phosphate dehydrogenase (EC 1.1.1.49) gene (zwf) of the cyanobacterium Synechococcus PCC 7942 was cloned on a 2.8 kb Hind III fragment. Sequence analysis revealed an ORF of 1572 nucleotides encoding a polypeptide of 524 amino acids which exhibited 41% identity with the glucose-6-phosphate dehydrogenase of Escherichia coli.     

Nitrite reduction in barley-root plastids: Dependence on NADPH coupled with glucose-6-phosphate and 6-phosphogluconate dehydrogenases,and possible involvement of an electron carrier and a diaphorase

Plastids from roots of barley (Hordeum vulgare L.) seedlings were isolated by discontinuous Percoll-gradient centrifugation. Coinciding with the peak of nitrite reductase (NiR; EC 1.7.7.1, a marker enzyme for plastids) in the gradients was a peak of a glucose-6-phosphate (Glc6P) and NADP⁺-linked nitrite-reductase system. High activities of phosphohexose isomerase (EC 5.3.1.9) and phosphoglucomutase (EC 2.7.5.1) as well as glucose-6-phosphate dehydrogenase (Glc6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) were also present in the isolated plastids. Thus, the plastids contained an overall electron-transport system from NADPH coupled with Glc6PDH and 6PGDH to nitrite, from which ammonium is formed stoichiometrically. However, NADPH alone did not serve as an electron donor for nitrite reduction, although NADPH with Glc6P added was effective. Benzyl and methyl viologens were enzymatically reduced by plastid extract in the presence of Glc6P+ NADP⁺. When the plastids were incubated with dithionite, nitrite reduction took place, and ammonium was formed stoichiometrically. The results indicate that both an electron carrier and a diaphorase having ferredoxin-NADP⁺ reductase activity are involved in the electron-transport system of root plastids from NADPH, coupled with Glc6PDH and 6PGDH, to nitrite.Abbreviations Cyt cytochrome - Glc6P glucose-6-phosphate - Glc6PDH glucose-6-phosphate dehydrogenase - MVH reduced methyl viologen - NiR nitrite reductase - 6PG 6-phosphogluconate - 6PGDH 6-phosphogluconate dehydrogenase     

Glucose-6-Phosphate Dehydrogenase/6-Phosphogluconate Dehydrogenase Ratio and the Glucose-6-Phosphate, 6-Phosphogluconate and Fructose-6-Phosphate Contents in Tobacco Plants Infected with Potato Virus Y

The ratio of activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (G6P DH/6PG DH), and the contents of glucose-6-phosphate (G6P), 6-phosphogluconate (6PG) and fructose-6-phosphate (F6P) were studied at various stages of potato virus Y (PVY) multiplication in Nicotiana tabacum cv. Samsun. G6P DH/6PG DH increased through the experiment from 0.42 to 0.53 in leaves of healthy tobacco, and up to 0.59 in PVY systemically infected leaves. However, these ratios in the ruptured protoplast preparations, and the chloroplast and cytosol fractions of healthy protoplasts were similar to that from infected ones. The ratio lower than 1, found in the healthy and/or PVY- infected leaf tissues and in the infected protoplasts as well, confirms the assumption that G6P DH is the control enzyme of oxidative pentosephosphate pathway not only in the healthy but also in the infected plants. The contents of G6P, 6PG and F6P in the period of the highest PVY multiplication were strongly decreased (to 30 – 50 % when compared with control healthy leaves) and were negatively correlated with the G6P DH and 6PG DH activities.     

Studies on the metabolism of galactose-6-phosphate in rat heart and brain.

The subcellular distribution of NADP⁺ and NAD⁺-dependent glucose-6-phosphate and galactose-6-phosphate dehydrogenases were studied in rat liver, heart, brain, and chick brain. Only liver particulate fractions oxidized glucose-6-phosphate and galactose-6-phosphate with either NADP⁺ or NAD⁺ as cofactor. While all of the tissues examined had NADP⁺-dependent glucose-6-phosphate dehydrogenase activity, only rat liver and rat brain soluble fractions had NADP⁺-dependent galactose-6-phosphate dehydrogenase activity. Rat liver microsomal and rat brain soluble galactose-6-phosphate dehydrogenase activities were kinetically different (K_m's 0.5 mm and 10 mm, respectively, for galactose-6-phosphate), although their reaction products were both 6-phosphogalactonate. Rat brain subcellular fractions did not oxidize 6-phosphogalactonate with either NADP⁺ or NAD⁺ cofactors but phosphatase activities hydrolyzing 6-phosphogalactonate, galactose-6-phosphate and galactose-1-phosphate were found in crude brain homogenates. In addition, galactose-6-phosphate and 6-phosphogalactonate were tested as inhibitors of various enzymes, with largely negative results, except that 6-phosphogalactonate was a competitive inhibitor (K_i = 0.5 mM) of rat brain 6-phosphogluconate dehydrogenase.     

Light mediated regulation of nitrate assimilation in Synechococcus leopoliensis

Synechococcus leopoliensis was cultivated in a light/dark regime of 12:12 h. After onset of the illumination (2 h), the specific activity of nitrite reductase, glutamine synthetase and isocitric dehydrogenase increased; that of glucose-6-phosphate dehydrogenase decreased and that of nitrate reductase and NAD- (NADP) glutamate dehydrogenase remained nearly unchanged.This stimulation of the enzymes in vivo was also observed in vitro. Also, when extracts from darkened cells were incubated with thioredoxin and dithioerythriol enzyme activities increased in the same amount as obtained in vivo. In addition, glucose-6-phosphate dehydrogenase and isocitric dehydrogenase were stimulated by Mn²⁺ and Mg²⁺ in the assay mixture. Glutamine synthetase activity was enhanced only by Mg²⁺ while Mn²⁺ was inhibitory.The results are discussed with respect to the regulation of nitrogen metabolism by light.Abbreviations GS glutamine synthetase - GOGAT glutamate-oxoglutarate-aminotransferase - TR thioredoxin - DTE dithioerythritol - LD change from light to dark     

Activity dynamics of potential marker enzymes of <Emphasis Type="Italic">Serratia marcescens</Emphasis> cytoplasm and periplasm

Activity dynamics of glucose-6-phosphate dehydrogenase, alkaline phosphatase, β-galactosidase and β-lactamase in the course of growth and development of Gram-negative bacteria Serratia marcescens was studied. Glucose-6-phosphate dehydrogenase can serve as a marker of cytoplasm and be also used as a marker of plasma membrane continuity. Alkaline phosphatase is a marker of periplasm. Glucose-6-phosphate dehydrogenase, β-lactamase and β-galactosidase can be additionally used as markers of the outer membrane continuity of microbial cells.     

Glucose metabolism by brown trout peripheral blood lymphocytes

Glucose metabolism in peripheral blood lymphocytes from the brown trout Salmo trutta has been studied. Glucose is taken up by means of a sodium-independent saturable process (K _m=10.8 mmol·l^-1), as well as by simple diffusion. Once within the cell, most of glucose is directed to lactate production through either the Embden-Meyerhof pathway or the hexose-monophosphate shunt. Rates of lactate formation are higher than rates of CO₂ formation. Glutamine does not exert an effect on either glucose uptake or glucose metabolism. The present study provides information regarding the nature of energy sources for different cell types in salmonids.Abbreviations 3-OMG 3-O-methyl glucose - EM Embden-Meyerhoff pathway - G6D glucose-6-phosphate dehydrogenase - HK hexokinase - HMS hexose monophosphate shunt - ICDH isocitrate dehydrogenase - K _m apparent Michaelis constant - LDH lactate dehydrogenase - MCB modified Cortland buffer - PBL peripheral blood lymphocytes - PFK fructose-6-phosphate kinase - PK pyruvate kinase - RBC red blood cells - V _max maximal rate of uptake     

Changes of some enzymatic activities in iodoacetate-treated microconidiating cultures of Neurospora crassa

In iodoacetate-treated microconidiating cultures of Neurospora crassa, mycelial yield, sucrose consumption and ethanol production are reduced. The specific activity of glyceraldehyde-3-phosphate dehydrogenase is sharply decreased while the specific activities of glucose-6-phosphate dehydrogenase and of 6-phosphogluconate dehydrogenase are stimulated. A polyphenoloxidase is induced in the microconidiating cultures.     

The screening of the enzyme and isoenzyme patterns in seeds ofAllium cepa L.

The screening of enzyme patterns in seeds ofAllium cepa cv. Všetatská revealed the presence of the following enzymes: alcohol dehydrogenase, lactate dehyd ogenase, NAD+- and NADP+-glyceraldehyde-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase NAD+- and NADP+-malate dehydrogenase, NADH₂- and NADPH₂-tetrazolium reductase catalase, Superoxide dismutase, acid and alkaline phosphatase, L-leucine aminopeptidase, glutamate dehydrogenase, non-specific esterase, and cholinesterase. Altogether 17 enzymes were detected in onion seeds, nine of which had more than three isoenzymes, NAD+-malate dehydrogenase had 8, and non-specific esterase 9 isoenzymes. The demonstration of cholinesterase and Superoxide dismutase activities is remarkable.     

Heterotrophic capacities of Plectonema boryanum

Acquisition of the dark heterotrophic growth capacity on glucose in Plectonema boryanum involves both adaptation and enrichment of a fast-growing genotype. The adaptation includes induction of functions involved in glucose incorporation and increase in glucose-6-phosphate dehydrogenase activity. Photosynthetic products are implicated in the control of both systems. Efficient energy conversion in the dark, as measured by cyanophage multiplication, correlates in time with the increase in potential for glucose incorporation while heterotrophic growth capacity correlates with the increase in glucose-6-phosphate dehydrogenase activity. The lower efficiency of heterotrophic growth compared to photoautotrophic growth is discussed in light of the conservation of the photosynthetic potency in the heterotrophic cells.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DTT dithiothreitol - G6P glucose-6-phosphate - NADP nicotinamide adenine dinucleotide phosphate - NTG N-methyl-N-nitro-N-nitrosoguanidine - RUDP ribulose-1,5-diphosphate - TCA trichloroacetic acid Dedicated to Prof. R. Y. Stanier on the occasion of his 60th birthday