Direct adaptation of cells to temperature: Similar changes of LDH isozyme patterns by in vitro and in situ adaptations in Xenopus laevis

• 1.1. Cells of Xenopus laevis were cultured in vitro chronically at different temperatures and their isozyme patterns of lactate dehydrogenase (LDH) were compared with those of liver of temperature-acclimated toads.
• 2.2. Relative increase of cathodic isozyme by cold adaptation was observed both in two independent cell lines and in toad tissue.
• 3.3. This supports the concept that adaptation of cells to local body temperature would be responsible to the change in isozyme pattern by temperature adaptation of organisms.
• 4.4. Such changes would not be a direct result of elevated pO₂, judging from tissue distribution of isozymes.

     

Light-induced effects of several enzymes of carbohydrate metabolism in Phycomyces blakesleeanus

• 1.1. The photoregulation shown by glyceraldehyde 3-phosphate dehydrogenase and glucose 6-phosphate dehydrogenase appears to be independent of the mad gene product(s) and also independent of carotene biosynthesis regulation.
• 2.2. The photoregulation of malate dehydrogenase appeared to be dependent on the mutation of the mad and car S genes.
• 3.3. Pyruvate kinase and lactate dehydrogenase may be classified as light-independent.
• 4.4. The action of ATP and fructose 1,6-bisphosphate on the enzymes studied was generally independent of light/dark grown conditions.
• 5.5. However, the effect of fructose 1,6-bisphosphate on Phycomyces pyruvate kinase appears to be light-dependent.

     

On the comparative turnover rates of the lactate dehydrogenase isozymes in rat tissues

• 1.1. An affinity chromatography technique for the determination of turnover parameters has been utilized for the derivation of new data for lactate dehydrogenase and its isozymes in a wide variety of tissues from female rats.
• 2.2. This methodology allowed the establishment of relative turnover characteristics in all tissues examined, and the evaluation of rate constants for synthesis and degradation and half-life values in the majority of these enzyme sources.
• 3.3. Considerable variation was evident in the turnover characteristics of total protein and lactate dehydrogenase in the different tissues, with the synthesis of the enzyme being highest in reproductive tissues, heart and liver, and degradation most prominent in reproductive tissues.
• 4.4. With regard to the isozymes, marked differences in half-lives were evident not only between the same isozyme in different tissues, but also between the various isozymes in any one tissue.
• 5.5. Bi-directional trends in the half-life values for the isozyme sequences in several tissues, indicated a distinctive contribution to turnover from the different cell types present.
• 6.6. These data have been discussed in relation to the available comparisons in the literature, and the known physiological correlations of lactate dehydrogenase in these tissues.

     

The erythrocytes of the metallic skink Niveoscineus metallicus

• 1.1. We studied the haemoglobin content, erythrocyte indices, erythrocyte enzymes and haemoglobin electrophoresis patterns of the metallic skink Niveoscineus metallicus and compared them to the small amount of published data on other small lizards.
• 2.2. Haemoglobin was much lower than that recorded for the salamander.
• 3.3. Erythrocyte enzymes (glucose phosphate isomerase and glucose 6 phosphate dehydrogenase) were lower in the skink than in the salamander. Glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase and pyruvate kinase were much higher in the skink than in the salamander.
• 4.4. A single, slow, haemoglobin component was identified by electrophoresis.

     

Possibilities of biochemical taxonomy of bats using hemoglobin,lactate dehydrogenase,esterases and other proteins

• 1.1. Bat hemoglobin resembles other mammalian Hb's in its physiological properties, and Hb differences among bat species are minor.
• 2.2. One polymorphism of the H chain of lactate dehydrogenase occurs in Myotis lucifugus and M. keenii, and another occurs in Eptesicus fuscus. Bat heart and muscle have identical LDH isozyme profiles.
• 3.3. Esterases and major low ionic strength extractabe proteins show a number of differences at the generic level, as well as some polymorphisms which cross species lines.
• 4.4. The protein studies indicate that bats have great individual variation, often of a type comparable to known genetically based protein polymorphisms in other species, but apparently have not had time to accumulate extensive divergent species specificity.

     

Variations in the lactate dehydrogenase activity during the development of the shrimp Palaemon serratus

• 1.1. The lactate dehydrogenase (LDH) from Palaemon serratus muscle has been studied throughout the development of the animal.
• 2.2. Enzymatic activities have been traced by polyacrylamide gel electrophoresis and kinetic studies.
• 3.3. The existence of two enzymes (L₁ and L₂) has been demonstrated.
• 4.4. During the larval development, both L₁ and L₂ remain at a low level.
• 5.5. After the larvae hatch L₁ and L₂ gradually rise although L₁ is predominant.
• 6.6. Measurement of kinetic parameters shows that the general behaviour of the enzymes of the embryo resembles that of the adult enzymes.
• 7.7. However, one can observe during the development a constant increase in the affinity of the enzyme towards its substrate, lactate.

     

NAD(P)H dehydrogenase from rabbit and rat liver: Purification and some properties

• 1.1. NAD(P)H dehydrogenase from rabbit liver was purified to electrophoretic homogeneity using a procedure also found applicable for the rat liver enzyme.
• 2.2. Rabbit and rat liver enzymes showed different behaviour in isoelectric focusing and different K_m values and turnover numbers.
• 3.3. Both enzymes were inhibited to similar extents by warfarin.
• 4.4. The rabbit enzyme is composed of two subunits of mol. wt 27,000 and contained 1 FAD group per subunit.
• 5.5. Some absorption and circular dichroism properties of the rat enzyme are shown.

     

Novel amino acid linked dehydrogenase in the sponge Halichondria panicea (pallas)

• 1.1. The sponge Halichondria panicea has a complete sequence of glycolytic and tricarboxylic acid cycle enzymes.
• 2.2. However, there is no detectable lactate dehydrogenase in H. panicea and lactate dehydrogenase appears to be functionally replaced by an enzyme which catalyses the reductive condensation of pyruvate and glycine to yield 2-methylimino-diacetic acid (strombine).
• 3.3. The intracellular distribution and kinetic properties of this novel enzyme (strombine dehydrogenase) have been investigated and its role in metabolism is discussed.

     

The breakdown of Tetrahymena ribosomes by lysosomal enzymes: Inhibition by cytosol

• 1.1. Extracts from Tetrahymena lysosomes contained acid RNase and proteinase. At pH 7.4 there was appreciable proteinase activity which was inhibited by a heat-stable protein present in cell sap.
• 2.2. Lysosomal enzymes rapidly converted 80S ribosomes to subunits at pH 7.4. Hydrolysis of ribosomal RNA was very slow at pH 7.4 but rapid at pH 5.0.
• 3.3. These reactions were inhibited by proteinase inhibitors and by cell sap, but the latter was relatively ineffective at pH 5.0.
• 4.4. It seems unlikely that ribosome breakdown in vivo is initiated by the release of lysosomal enzymes into the cytosol.

     

Agaricus bisporus tyrosinase—II. Characterization of hydroxylase and dehydrogenase activities

• 1.1. Preparative Isoelectric focusing (PIEF) was used to isolate hydroxylasic and dehydrogenasic activities, at different pI.
• 2.2. The fraction at pI 4.7 and 4.9 displays a pure dehydrogenase activity (substrate l-DOPA).
• 3.3. This fraction did not react with tyrosine, either in the spot-test or in absorption spectra (200–620 nm), and did not exhibit any oxygen consumption.
• 4.4. The fraction at pI 4.1 and 4.3 reacted with both l-DOPA and tyrosine as substrate, showing dehydrogenase and hydroxylase activity.
• 5.5. The latter activity was confirmed by the oxygen consumption test, showing that molecular oxygen is used to ortho-hydroxylate tyrosine.

     

Content and synthesis of several abundant glycolytic enzymes in skeletal muscles of normal and dystrophic mice

• 1.1. In both 2- and 3-month-old 129 ReJ mice, the catalytic activity levels of three enzymes involved in glycogen breakdown (phosphorylase, enolase, and aldolase) were found to be 35–50% lower in hind limb muscles of dystrophic mice as compared with normal mice.
• 2.2. The reduced activities of these enzymes in the diseased tissue was directly due to corresponcling reductions in the number of enzyme molecules rather than being due to inactivation of the enzymes in the dystrophic muscle.
• 3.3. Results of short term double isotope incorporation experiments conducted with muscle expiants in vitro suggested that the rates of synthesis of these enzymes, and of most other abundant cytosolic proteins, relative to each other, were similar in hind limb muscles of normal and dystrophic mice.
• 4.4. The present work on murine muscular dystrophy is discussed in terms of our previous studies into the influence of avian muscular dystrophy on the content and synthesis of abundant glycolytic enzymes in chicken skeletal muscles.

     

Activities of the three ammonia-forming enzymes in the tissues of the brackish-water bivalve Corbicula japonica

• 1.1. Activities of the three ammonia-forming enzymes, glutamate dehydrogenase, AMP deaminase and serine dehydrase (SerDH), were measured in tissues of gill, digestive diverticula, mantle and foot muscle of the brackish-water bivalve Corbicula japonica.
• 2.2. High levels of SerDH activity were detected in gill and digestive diverticula, while the activity levels of the other two enzymes were low.
• 3.3. The result suggests the significance of SerDH in amino acid degradation of this species.

     

Characterisation of the electron transport chain of an obligate methylotroph,strain 4025

• 1.1. The obligate methanol-utilising bacterium strain 4025 contains cytochromes b and c. Cytochrome a is never present.
• 2.2. The soluble cytochrome c is similar to that from other methylotrophs in reacting (slowly) with carbon monoxide and it can be separated into two types, differing markedly in their isoelectric points.
• 3.3. Some of the cytochrome b reacts rapidly with carbon monoxide and is thus the likely cytochrome oxidase (cytochrome o).
• 4.4. The partially purified, NAD⁺-independent methanol dehydrogenase is similar to such enzymes from the other methanol-utilising bacteria in respect of its prosthetic group, dependence on ammonia or methylamine for activity and its wide substrate specificity.
• 5.5. The fluorescence seen in colonies of this organism is probably due to a flavin derivative.
• 6.6. This study of electron transport components does not shed any light on the unusually high copper requirement shown by this methylotroph.

     

Ontogenic change of digestive enzymes in Penaeus monodon

• 1.1. Ontogenic changes of both proteases and carbohydrases of Penaeus monodon from different larva stages to adult were investigated.
• 2.2. Total protease activity was low during nauplius and zoea but peaked up in mysis. This was due to the activity increase of both trypsin and chymotrypsin.
• 3.3. The change of isozyme pattern of these two enzymes from different life stages of the shrimp was further determined by functional staining on an electrophoregram.
• 4.4. Activity of α-amylase increased after the post-larva stage, while that of chitinase and maltase showed a peak in zoea then gradually decreased to adult.
• 5.5. The ratio of α-amylase activity to protease coincided with the dietary change of the shrimp in different life stage.

     

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.

     

The haemocytes and the activities of leucine aminopeptidase and alkaline phosphatase during development of Ceratitis capitata: Specific secretion of a leucine aminopeptidase isozyme

• 1.1. The types of haemocytes during larval development were studied.
• 2.2. The developmental profile of leucine aminopeptidase and alkaline phosphatase was studied. The maximum LAP activity was found to be in early larval development, while the maximum alkaline phosphatase during the white pupal stage.
• 3.3. These activities were compared with those determined in cell-free haemolymph.
• 4.4. Both hydrolytic enzymes have been found histochemically in the prohaemocytes and in the plasmatocytes.
• 5.5. In cultured haemocytes experiments it was found that 64% of the total LAP activity was secreted into the incubation medium, while electrophoretic analysis of released LAP activity demonstrated that only LAP A isozyme was secreted.
• 6.6. Based on the above results we suggest that both hydrolytic enzymes are functionally important throughout larval development.

     

2-Deoxyglucose transport by the frog sartorius: Effects of electrical stimulation and N-carbobenzoxy-glycyl-l-phenylalaninamide

• 1.1. Studies characterizing glucose transport in the frog sartorius were performed.
• 2.2. For nonstimulated and stimulated muscles, intracellular 2-deoxyglucose exceeded 2-deoxyglucose-6-phosphate at 15 min, showed little further increase, and was maintained below the extracellular concentration for 2 hr.
• 3.3. Accumulated 2-deoxyglucose-6-phosphate did not inhibit glucose transport.
• 4.4. Unlike in adipocytes, basal and stimulated 2-deoxyglucose transport showed no difference in sensitivity to N-carbobenzoxy-glycyl-l-phenylalaninamide.
• 5.5. Phenylarsine oxide blocked contraction-enhanced 2-deoxyglucose uptake.
• 6.6. These results suggest that the glucose transporter of the sartorius exhibits auto-regulation, and that basal transport is not regulated by the same process as in adipocytes.

     

Isolation and characterization of lipoamide dehydrogenase from mackerel dark muscle

• 1.1. Lipoamide dehydrogenase was purified 1500-fold from mackerel dark muscle.
• 2.2. The enzyme was homogeneous as judged by acrylamide gel electrophoresis in the presence and absence of SDS.
• 3.3. Molecular weights of 102,000 and 55,000 were estimated for the native and denatured enzyme, respectively.
• 4.4. Optimal activity for the enzyme was obtained at around pH 5.7 and enhanced with citri acid.
• 5.5. Loss of activity was less than 5% by incubating the enzyme at 70°C for 20 min.
• 6.6. An apparent K_m of 3.1 × 10⁻³ M was obtained for dl-lipoic acid and 1.5 × 10⁻⁵ M for NADH.
• 7.7. The properties of lipoamide dehydrogenase from mackerel dark muscle observed in this investigation were very similar to those reported for the enzyme from other sources.

     

Enzymes of fructose metabolism in the intestinal mucosa of the rat (Rattus norvegicus). Localization along the small intestine; consequences of dietary fructose

• 1.1. The activities of all the eight enzymes of conversion of fructose to glucose, of all the three key enzymes of glycolysis and of the two dehydrogenases of pentose shunt were determined in proximal and distal mucosa of small intestine.
• 2.2. With the exception of hexokinase, all of these enzymes have an activity significantly higher in the proximal than distal mucosa.
• 3.3. The gradient along the intestine is particularly important for the three enzymes which are typical for fructose metabolism (ketohexokinase, triokinase and fructose-1-phosphate aldolase), for glucose-6-phosphatase and for phosphofructokinase.
• 4.4. The effects of fructose diet on the enzyme activities are compatible with the results, described in other papers, concerning the final products of metabolism.
• 5.5. The increase of fructose metabolism appears to result mainly from the stimulation of the activities of ketohexokinase and fructose-1-phosphate aldolase which control all the pathways of ketohexose utilization.
• 6.6. The activation of glucose-6-phosphatase, in comparison with the other enzymes which are involved in glucose-6-phosphate metabolism, explains the appearance of the ability to synthesize glucose with fructose as substrate. This enzyme is the only key enzyme of fructose to glucose conversion which responds to fructose feeding in distal mucosa.
• 7.7. The activities of hexokinase and phosphofructokinase are not increased by fructose feeding.
• 8.8. The activity of pyruvate kinase. the only key glycolytic enzyme which is necessarily implicated when fructose is the substrate, is stimulated but less than the typical enzymes of fructose metabolism.
• 9.9. But, because of its quantitative importance, the glycolytic pathway is responsible for the most part of the observed increase of fructose utilization.
• 10.10. The responses of pyruvate kinase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities to fructose feeding are similar in the two parts of small intestine.
• 11.11. The activities of ketohexokinase, triokinase and glucose-6-phosphate isomerase are stimulated only in the proximal small intestine mucosa.
• 12.12. The other enzyme activities which are stimulated in proximal segment are also increased in distal segment.
• 13.13. All segments of small bowel show adaptive changes to dietary manipulation but not necessarily for all their functions.
• 14.14. The gradient of enzyme activities from the proximal to the distal small intestine persists despite dietary modification, but the data do not determine that this gradient is intrinsic or that it is not intrinsic.

     

Allozyme variation in the stingless bee Trigona fuscobalteata (hymenoptera,apidae) from Peninsular Malaysia

• 1.1. A population of Trigona fuscobalteata from Peninsular Malaysia was analysed for genetic variation at 9 gene-enzyme systems comprising 13 loci.
• 2.2. Two gene-enzyme systems (phosphoglucomutase and isocitrate dehydrogenase) were polymorphic in the 20 colonies studied.
• 3.3. Isocitrate dehydrogenase was represented by duplicate genes.
• 4.4. The number of loci for several enzyme systems appeared to be different from that reported for the Australian stingless bees.