Kinetic behaviour of chicken liver mitochondrial malate dehydrogenase and lactate dehydrogenase mixtures

• 1.1. In the mitochondria of chicken liver cells there is lactate dehydrogenase activity that catalyses the reduction of the oxaloacetate by the NADH.
• 2.2. The presence of lactate dehydrogenase in the malate dehydrogenase preparations causes an apparent activation in the double-reciprocal plot at high oxaloacetate concentrations that depends on the lactate dehydrogenase/malate dehydrogenase ratio in the preparation.
• 3.3. The separation of the two molecular forms of chicken liver mitochondrial malate dehydrogenase, free from lactate dehydrogenase, is described.

     

Kinetic mechanism of guinea-pig skeletal muscle lactate dehydrogenase (M4) with oxaloacetate-NADH and pyruvate-NADH as substrates

• 1.1. Guinea-pig skeletal muscle lactate dehydrogenase M₄ isoenzyme, with pyruvate and NADH as substrates, is adapted to an ordered bi-bi ternary complex mechanism at pH 7.0.
• 2.2. In the same conditions, the kinetic mechanism of the reaction, with oxaloacetate and NADH as substrates, is of the rapid equilibrium ordered bi-bi ternary complex type; NADH is the first substrate in the reaction sequence.

     

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.

     

Temperature acclimation in amphibians: Changes in lactate dehydrogenase activities and isoenzyme patterns in several tissues from adult Discoglossus pictus pictus (Otth.)

• 1.1. The effect of cold (8 ± 2°C) acclimation on the lactate dehydrogenase activities and isoenzyme patterns from sartorius muscle, liver, heart and brain of adult Discoglossus pictus pictus (Otth.) was studied.
• 2.2. Two groups of animals were studied: one set of animals was trapped in October and another set in December. In both cases some of the animals were sacrificed upon collection and some others subjected to 5 months of acclimation at 8 ± 2°C before being sacrificed for analysis.
• 3.3. A general trend towards a decrease in LDH specific activity was observed during cold acclimation. The magnitude of change, but not the direction, depends on both the tissue examined and the season at which the experiment was initiated.
• 4.4. A complex LDH isoenzyme reorganization was also found in liver, heart and brain. In liver from Experiment 1 and in heart from both experiments, a relative maintenance in M-type LDH activity during cold acclimation was observed. However, in brain there was a relative maintenance of LDH₃ activity in both experiments.
• 5.5. The low behavioral activity (and its metabolic consequences) and the existence of an intrinsic annual rhythm in D. pictus metabolism are suggested as responsible for the observed enzymatic changes.

     

Glycolytic enzymes of fowl and turkey spermatozoa

• 1.1. It was confirmed that, under anaerobic conditions, fowl spermatozoa formed lactate from glucose thirteen times faster than turkey spermatozoa.
• 2.2. The profiles of glycolytic enzyme activities were similar for spermatozoa from both species; however fowl spermatozoal activities were generally 2- to 4-fold higher.
• 3.3. Exceptions were glycerophosphate mutase and lactate dehydrogenase activities which were respectively 9.5 and 41 times greater in fowl spermatozoa.
• 4.4. In both species, spermatozoal glyceraldehyde-3-phosphate dehydrogenase had the lowest activity of the glycolytic enzymes.

     

Distribution of opine dehydrogenases and lactate dehydrogenase activities in marine animals

• 1.1. Opine dehydrogenases (OpDHs) and lactate dehydrogenase (LDH) activities were determined in various marine animals. OpDHs were detected in six marine invertebrate phyla; Porifera, Coelenterata, Annelida, Mollusca, Arthropoda and Echinodermata in phylogenic sequence.
• 2.2. Among several OpDHs, tauropine dehydrogenase (TaDH) occurred widely in marine invertebrates, from Porifera to Echinodermata.
• 3.3. With a few exceptions, total OpDHs activities exceeded that of LDH activity in the marine invertebrates investigated.
• 4.4. With respect to anaerobic glycolysis, OpDHs are indicated to play an important role in phylogenically lower invertebrates, whereas LDH is more important in higher animals.

     

Lactate dehydrogenase isozymes of the leopard danio,Brachydanio nigrofasciatus: their characterization and ontogeny

• 1.1. The tissue specific patterns and ontogeny of lactate dehydrogenase (LDH) are reported.
• 2.2. While all tissues (eye, brain, heart, intestine, liver, ovary and skeletal muscle) show isozymes of A and B subunit composition, only liver extracts possess isozymes resulting from C subunit synthesis.
• 3.3. The A₄ homopolymer appears simultaneously with initial muscle contractility and is correlated with the physiological function of muscular contraction.
• 4.4. The activation of the Ldh-C locus is correlated with the first functioning of liver. It is suggested that the state of differentiation of liver cells may be the stimulus required for C locus expression.

     

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.

     

Enzyme activities and level of SH groups in breast carcinomas

• 1.1. The carcinoma showed higher enzyme activities than the normal mammary tissue.
• 2.2. The ratios of glutamate dehydrogenase, glutathione reductase and catalase to lactate dehydrogenase were lower in carcinomas than in normal tissues. Similarly, the ratios of glutamate dehydrogenase, glutathione reductase and catalase to glucose-6-phosphate dehydrogenase were also significantly lower in carcinomas.
• 3.3. There were no significant differences in enzyme activities between stages I and II of disease, however in the metastatic tissues, there were significant differences between stages I and II.
• 4.4. SH groups were higher in the tissues of cancer patients than in normal tissues. The levels of thiols groups were higher in carcinomas at stage III of disease.

     

Distribution of beta-adrenergic binding in fractionated porcine adipocytes

• 1.1. The subcellular distribution of the porcine adipocyte beta-adrenergic receptor was studied in fractionated adipocytes.
• 2.2. The 30,000 g pellet obtained from hypotonically lysed cells contained membrane vesicles and mitochondria; it yielded approx 200–300 fmol dihydroalprenolol-bound receptors/mg protein.
• 3.3. Activity was increased to about 1000 fmol/mg protein after isolation of a plasma membrane fraction on a Percoll gradient.
• 4.4. The 5'-nucleotidase, succinate dehydrogenase and lactate dehydrogenase activities were usually enriched in compartments different from the ligand-binding activity.
• 5.5. Activity of porcine adipocyte 5'-nucleotidase, a purported plasma membrane marker enzyme, was not distributed in the same manner as the beta-adrenergic receptor.

     

Electrophoretic characterization of a hybrid between Eretmochelys imbricata and Caretta caretta (Cheloniidae)

• 1.1. An intermediate morphotype between Eretmochelys imbricata and Caretta caretta was studied in Praia do Forte, Bahia, Brazil.
• 2.2. Three enzymatic systems were successfully analyzed: SOD, lactate dehydrogenase (LDH) and esterase (EST). Isoelectric focusing of total soluble proteins of muscle and transferrin were shown.
• 3.3. Esterase exhibited nine phenotype patterns, seven in C. caretta and one in the others morphotypes. SOD phenotypes were identical in the three morphotypes. Lactate dehydrogenase and transferrins were characteristic for each species.
• 4.4. Jaccard's measure of similarity was calculated and a phenogram with the three morphotypes were constructed using isoelectric focusing of total soluble proteins.

     

Thermal stability of the molecular forms of guinea-pig skeletal muscle cytoplasmic malate dehydrogenase and kinetic mechanism of the thermostable form

• 1.1. Guinea-pig skeletal muscle cytoplasmic malate dehydrogenase appears under two molecular forms; the heating of the dialyzed soluble fraction of the tissue shows that the A form is stable at 55 C, while the B form is inactivated. Under these conditions, the lactate dehydrogenase M₄ isoenzyme becomes considerably unstable; nevertheless, its activity is notably preserved with NADH.
• 2.2. The reaction kinetic mechanism of the isolated A form has been determined (pH 7.4), enabling the nature of the abortive complexes and the values of K_eeq and of ΔG°′ of the reaction to be determined.

     

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.

     

Purification,isolation and characterization of a phosphoglycolate phosphatase isoenzyme from human erythrocytes

• 1.1. Preparation, purification and characterization of a phosphoglycolate phosphatase (PGP)3 isoenzyme from human erythrocytes was achieved by DEAE-Sepharose CL.-6B chromatography and isoelectric focusing using carrier ampholytes. pH 4–6.
• 2.2. The isoenzyme has an isoelectric point of 5.00 ± 0.05 and could be purified 33.000 fold to a specific activity of 32.7 U/mg of protein. It represents the PGP phenotype 1 consisting of a single isoenzyme.
• 3.3. The enzyme is composed of two subunits (mol. wt 35,000) which are identical and not connected by SS-bridges.
• 4.4. At 4°C the isoenzyme is more stable in the pH range of 7–9 than at acid pH values.
• 5.5. Incubation at 30 and 40°C for 4 hr does not affect the activity of the isoenzyme.
• 6.6. It has a K_m-value of 0.28 mM for phosphoglycolate (PG) as substrate.

     

Allozyme variation in the solanaceous fruit fly Bactrocera latifrons (insecta: diptera: tephritidae) from peninsular malaysia

• 1.1. Bactrocera latifrons fruit flies recovered from four solanaceous fruits (Capsicum annuum, Lycopersicon esculentum, Solanum pseudocapsicum and Solanum melongena) in Peninsular Malaysia were analyzed for a total of 15 gene-enzyme systems comprising 21 loci.
• 2.2. Eleven loci—aAdh, Aldox, Ald, Est-F, Est-S, Hk-F, Ldh, cMdh, Me, Pep-A and Pep-C—were invariant.
• 3.3. Of the polymorphic loci, cathodal alcohol dehydrogenase, glucose phosphate isomerase, glycerol-3-phosphate dehydrogenase, hydroxybutyrate dehydrogenase, isocitrate dehydrogenase, anodal malate dehydrogenase and phosphoglucomutase were represented by two alleles each, while hexokinase-S, peptidase-B and phosphogluconate dehydrogenase were represented by three alleles each.
• 4.4. The proportion of polymorphic loci ranged from 0.28 to 0.33, while the mean heterozygosity ranged from 0.04 to 0.13.
• 5.5. The genetic variability is associated with the host range.

     

The effect of hypoxia on carbohydrate metabolism in flounder (Platichthys flesus L.)—II. High energy phosphate compounds and the role of glycolytic and gluconeogenetic enzymes

• 1.1. ATP, ADP, AMP, energy charge potential and total adenylates in heart, kidney and muscle are relatively unaffected by environmental hypoxia. In the liver, hypoxia causes a 90% drop in ATP, a rise in ADP and AMP, and a drop in energy charge potential and total adenylates. In the muscle tissue ATP concentration is stabilized by a large creatine phosphate pool.
• 2.2. Hexokinase activity in the heart is 20 times higher than in the swimming muscle, and thus the heart has a high potential for utilizing exogenous glucose as an anaerobic substrate.
• 3.3. The role of creatine phosphate in regulating muscle glycolysis is discussed on background of the strong inhibition of muscle phosphofructokinase by physiological concentrations of creatine phosphate.
• 4.4. Flounder heart has a dominating M-type lactate dehydrogenase which is identical to the muscle enzyme by electrophoretic and kinetic criteria. This improves the anaerobic capabilities of the flounder heart compared to other fish hearts.
• 5.5. Both liver and kidney have high activities of the gluconeogenetic enzymes glucose-6-phosphatase, fructose-1,6-diphosphatase, and phosphoenolpyruvate carboxykinase and both are capable of synthesizing glucose from [¹⁴C]lactate. Because of more favorable energy conditions in the kidney this organ may substitute the liver as a gluconeogenetic organ during hypoxia.

     

Role of glutamate dehydrogenase reaction in the control of citrate pool in yeast

• 1.1. Role of NADP-glutamate dehydrogenase in the depletion of citrate was analyzed using permeabilized yeast cells.
• 2.2. Citrate was converted to 2-oxoglutarate, which was then metabolized to glutamate by NADP-glutamate dehydrogenase in the presence of ammonium ion.
• 3.3. Formation of 2-oxoglutarate plus glutamate was in good agreement with the concentration of citrate decreased. Glutamate formation can be a good indicator of the depletion of citrate, because 70% of the citrate decreased was converted to glutamate.
• 4.4. Glycolytic activity was closely correlated with the decrease in citrate under the in situ conditions.
• 5.5. NADP-glutamate dehydrogenase increased in anaerobically grown yeast cells.
• 6.6. An effective depletion of citrate by increased synthesis of NADP-glutamate dehydrogenase can explain the lowered mechanism of citrate causing glycolytic stimulation under the anaerobic growth conditions of yeast.

     

1H NMR study of metabolic alterations in the small intestine of rats infected with Hymenolepis diminuta

• 1.1. 1H NMR spectra of the duodenum, jejunum and ileum tissues of the small intestine of a rat showed metabolic gradients.
• 2.2. The concentrations of metabolites in these gut regions were altered by the presence of the tapeworm Hymenolepis diminuta.
• 3.3. In the infected duodenum there was significantly less glycogen, glucose and phosphocreatine/creatine, but significantly more lactate than in the corresponding controls.
• 4.4. Infected jejunum contained significantly less betaine but significantly more succinate, alanine and lactate.
• 5.5. Infected ileum had significantly less glycogen and taurine but significantly more alanine and lactate.

     

Interaction of lipogenic substrates in porcine adipose tissue in vitro

• 1.1. Porcine adipose tissue was incubated with radiolabeled glucose, acetate or lactate. Saturation curves indicated that lactate > glucose > acetate in providing two-carbon units for fatty-acid synthesis.
• 2.2. Competition between individual substrates indicated that lactate was the best lipogenic substrate.
• 3.3. Incubation of all three substrates at concentrations observable in serum indicated that at 5.56mM, glucose was the preferred lipogenic substrate in the presence of 0.1 mM acetate and 1.0 mM lactate.
• 4.4. At elevated concentrations (18.52mM glucose, 1.0 mM acetate and 10.0 mM lactate), acetate and lactate were preferred to glucose as lipogenic substrates.

     

A one-step pmr determination of hydrogen transfer stereospecificity of NADP+-linked oxidoreductases

• 1.1. A simple, facile one-step method has been devised to measure the stereospecificity of NADP⁺-linked oxidoreductases. The procedure involves coupling the test enzymes to enzymes of known stereospecificity in the presence of deuterated substrates. The regenerated NADP⁺ in the coupled reactions is analyzed by PMR for its deuterium content at the carbon-4 position of the nicotinamide ring.
• 2.2. It is found that malate dehydrogenase (EC 1.1.1.37). lactate dehydrogenase (EC 1.1.1.27) and glycerate dehydrogenase (EC 1.1.1.29) are A-side stereospecific whereas glutamate dehydrogenase (EC 1.4.1.3) and glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) are B-side stereospecific.
• 3.3. Enzymes which can utilize both NAD⁺ and NADP⁺ have the same stereospecificity with respect to the coenzyme.