Lactate and malate dehydrogenase in the fan-shell associated shrimp, Pontonia pinnophylax (Otto): Effects of temperature and urea

In Pontonia pinnophylax (Otto), a crustacean decapod inhabiting the mantle cavity of Pinna nobilis L. (Bivalvia: Pteriomorpha), the lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activity, and their electrophoretic patterns, were compared in relation to heat and urea inactivation. Activity was higher in LDH than in MDH, and the electrophoretic patterns showed a predominance of LDH-A4 and the presence of both mitochondrial and cytosolic MDH. Heat incubation reduced both enzymatic activities, but more MDH. Also all isozymes showed different heat sensitivity, with anodic forms more heat-resistant than cathodic ones, either in LDH as in MDH. Urea treatment caused also a higher inactivation of the most cathodic isozymes, but MDH appeared more resistant than LDH at 2 M urea. The high polymorphism of these enzymes suggests an adaptation of Pontonia metabolism to hypoxic conditions; moreover, the different isozyme stability grade should be functional to contrast environmental variability.     

Malate/lactate dehydrogenase in mollicutes: evidence for a multienzyme protein

The malate (MDH) and lactate (LDH) dehydrogenases belong to the homologous class of 2-ketoacid dehydrogenases. The specificity for their respective substrates depends on residues differing at two or three regions within each molecule. Theoretical peptide-mass fingerprinting and PROSITE analysis of nine MDH and six LDH molecules were used to describe conserved sites related to function. A unique LDH is described which probably also confers MDH activity within the 580 kbp genome of Mycoplasma genitalium (class: Mollicutes). A single hydrophilic arginine residue was found in the active site of the M. genitalium LDH enzyme, differing from an hydrophobic residue normally present in these molecules. The effect of this residue may be to alter active site substrate specificity, allowing the enzyme to perform two closely related tasks. Evidence for a single gene affording dual enzymatic function is discussed in terms of genome size reduction in the simplest of free-living organisms. Since Mollicutes are thought to lack enzymes of the tricarboxylic acid cycle that would otherwise bind and interact with MDH in bacterial species possessing this pathway, active site modification of M. genitalium LDH is the sole requirement for MDH activity of this molecule. The closely related helical Mollicute, Spiroplasma melliferum, was shown to possess two distinct gene products for MDH/LDH activity.     

Enzymatic urea adaptation: lactate and malate dehydrogenase in elasmobranchs

Lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) electrophoretic tissue patterns of two different orders of Elasmobranchii: Carchariniformes (Galeus melanostomus and Prionace glauca) and Squaliformes (Etmopterus spinax and Scymnorinus licha) were studied. The number of loci expressed for these enzymes was the same of other elasmobranch species. Differences in tissue distribution were noted in LDH from G. melanostomus due to the presence of an additional heterotetramer in the eye tissue. There were also differences in MDH. In fact, all the tissues of E. spinax and G. melanostomus showed two mitochondrial bands. Major differences were noted in the number of isozymes detected in the four compared elasmobranchs. The highest polymorphism was observed in E. spinax and G. melanostomus, two species that live in changeable environmental conditions. The resistance of isozymes after urea treatment was examined; the resulting patterns showed a quite good resistance of the enzymes, higher for LDH than MDH, also at urea concentration much greater than physiological one. These results indicated that the total isozyme resistance can be considered higher in urea accumulators (such as elasmobranchs) than in the non-accumulators (such as teleosts).     

Lactate dehydrogenase X, malate dehydrogenase and total protein in rat spermatozoa during epididymal transit

Lactate dehydrogenase isozyme X (LDH X), malate dehydrogenase (MDH) and total soluble protein have been determined in lysates of spermatozoa isolated from caput, corpus and cauda of rat epididymis. Transit of spermatozoa through epididymis is accompanied by a reduction of LDH X, MDH and total protein per cell in sexually rested animals. The profiles of reduction along epididymal segments are different for the three variables studied. Mating with receptive females during the 5 days prior to determinations increases significantly the levels of MDH in spermatozoa from all sections of epididymis and produces increase of total soluble protein in the cells contained in cauda.     

Polymorphism of malate dehydrogenase in Ascaris suum

Starch gel electrophoresis of homogenates prepared from adult Ascaris suum revealed polymorphism for the number, staining intensity, and electrophoretic mobility of the cytoplasmic isozymes of malate dehydrogenase (MDH). Five different variant isozymic patterns were found among the 2160 worms surveyed. The most acceptable formulation for the molecular basis of the variant patterns supports the hypothesis that the synthesis of supernatant MDH in Ascaris suum is under the control of two separate genetic loci, MDH _A and MDH _B.This work was supported by National Institutes of Health Grant HD-00994.     

Functional interrelations between isozymes of dehydrogenases in the intact and denervated rabbit muscles]

A correlation is shown to exist between malate dehydrogenase (MDH), lactate dehydrogenase (LDH) and glycerol-3-phosphate dehydrogenase (glycerol-3-PDH activity values, lactate/pyruvate and malate/oxaloacetate coefficients, MDH and LDH isozyme spectra and kinetic properties of LDH isozymes in soluble fractions of cytoplasm from intact rabbit m. soleus (red), m. gastrocnemius (mixed) and m. quadratus lumborum (white). In denervated soleus and gastrocnemius the cytoplasmic MDH/LDH, mitochondrial MDH/LDH, MDH mitochondrial/MDH cytoplasmic activity ratios, concentrations of substrates and isozyme spectra of MDH and LDH tend to equalize. The obtained results indicate the importance of isozyme composition and total activity ratios of the dehydrogenases for regulation of pyruvate and NADH metabolic pathways.     

Influence of L-thyroxine upon enzymatic activity in the renal tubular epithelium of the rat under normal conditions and mercury-induced lesions. II. Histochemical studies of lactate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, unspecific esterase, and glucose-6-phosphate dehydrogenase.

Mercury-induced renal tubular lesions in the rat present histochemically with a decrease of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G-6-PD), and unspecific esterase (UE), but with an increase of lactate dehydrogenase (LDH), indicating a drop of energy supply as well as a switch from oxidative to glycolytic energy production. L-thyroxine has the same effect on SDH, G-6-PD, and LDH, but an inverse effect on MDH and UE, pointing to stimulation of gluconeogenesis. However, administration of L-thyroxine to animals which have been submitted to sublimate intoxication even further decreases the MDH and UE activity while raising or partly restoring the activity of LDH, SDH, and G-6-PD. This observation is interpreted as an attempt of the damaged epithelial cell, as the gluconeogenesis ceases, to gain relatively more energy supply for the benefit of the vitally indispensable tubular Na+ reabsorption.     

The isozymes of lactate dehydrogenase, malate dehydrogenase and glucosephosphate isomerase in Italian ictalurids

1. The isozymes of lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and glucose-phosphate isomerase (GPI) of three species of Italian ictalurids: Ictalurus sp., I. nebulosus marmoratus, and I. punctatus, were analyzed. 2. Isoelectric focusing (IEF) was applied to polyacrylamide gel plates, and the isozymes revealed by means of specific histochemical staining. 3. Species-specific monomorphic patterns were found for LDH. 4. In contrast, MDH and GPI have the same patterns in I. sp. and I. nebulosus marmoratus and different patterns in I. punctatus. 5. Comparison of the isozymatic patterns of the three species clearly showed the close relationship between I. sp. and I. nebulosus marmoratus and the relative taxonomic distance of I. punctatus, and thus the early detachment of this last species from a presumptive common ancestral lineage.     

Histochemical changes in rat sperm malate dehydrogenase activity during passage through epididymis

Histochemical activity of malate dehydrogenase (MDH: E.C. 1.1.1.37) in rat sperm mitochondria decreased during the epididymal transit of sperm. In an electrophoretic study two major MDH isozymes (MDH-A and MDH-B) were demonstrated in the sperm. The epididymal sperm showed two minor isozymes associated with MDH-A, while the testicular sperm did not.     

Alfalfa malate dehydrogenase (MDH): molecular cloning and characterization of five different forms reveals a unique nodule‐enhanced MDH

Malate dehydrogenase (MDH) catalyzes the readily reversible reaction of oxaloacetate ; malate using either NADH or NADPH as a reductant. In plants, the enzyme is important in providing malate for C ₄ metabolism, pH balance, stomatal and pulvinal movement, respiration, β-oxidation of fatty acids, and legume root nodule functioning. Due to its diverse roles the enzyme occurs as numerous isozymes in various organelles. While antibodies have been produced and cDNAs characterized for plant mitochondrial, glyoxysomal, and chloroplast forms of MDH, little is known of other forms. Here we report the cloning and characterization of cDNAs encoding five different forms of alfalfa MDH, including a plant cytosolic MDH (cMDH) and a unique novel nodule-enhanced MDH (neMDH). Phylogenetic analyses show that neMDH is related to mitochondrial and glyoxysomal MDHs, but diverge from these forms early in land plant evolution. Four of the five forms could effectively complement an E. coli Mdh^– mutant. RNA and protein blots show that neMDH is most highly expressed in effective root nodules. Immunoprecipitation experiments show that antibodies produced to cMDH and neMDH are immunologically distinct and that the neMDH form comprises the major form of total MDH activity and protein in root nodules. Kinetic analysis showed that neMDH has a turnover rate and specificity constant that can account for the extraordinarily high synthesis of malate in nodules.      

Soluble and chloroplast malate dehydrogenase isoenzymes of Triticum aestivum

Three isoenzymes of malate dehydrogenase have been isolated from 9-day-old wheat shoots. The microbody (peroxisome) and chloroplast MDH are similar in their electrophoretic behaviour. The mitochondrial MDH, soluble MDH and chloroplast MDH differ in K_m values for malate and NAD. The activity of MDH isoenzymes with NAD⁺-analogues as substrate was in the order 3-AP-NAD⁺ > 3-AP-deam NAD⁺ > NAD⁺ > TN-NAD⁺ and deam NAD⁺. The thermal stabilities of the isoenzymes were significantly different: C-MDH > m-MDH > S-MDH.     

The role of malate dehydrogenase in adaptation to hypoxia in invertebrates]

In muscle tissue of lamellibranch molluscs and crustaceans (cf. Table for the species studied), high levels of malate dehydrogenase and low ones of lactade dehydrogenase were detected. There is a direct relationship between the value of MDH/LDH ratio and the capacity of organisms to withstand temporary anaerobiosis. Animals with high ratio may adapt to hypoxia by transition from aerobic metabolism to anaerobic one.     

Kinetic analysis of duck epsilon-crystallin with L-lactate dehydrogenase activity: determination of kinetic constants and comparison of substrate specificity.

A systematic analysis of the kinetic properties of duck lens epsilon-crystallin with lactate dehydrogenase [LDH, (E.C. 1.1.1.27)] activity was carried out by employing some 19 different alpha-keto acids as substrates for this NADH-dependent LDH-catalyzed reaction. The steady-state Michaelis and catalytic constants (Km, kcat) were determined for a broad range of organic compounds. The results provide important insights regarding the binding and affinity of substrates to active sites of this enzyme crystallin and indicate a great potential for the application of the stable epsilon-crystallin as a catalyst to the synthesis of some important chiral alpha-hydroxyacids in a convenient and efficient way. It is also demonstrated for the first time that in addition to the enzymatic activity of lactate dehydrogenase, duck epsilon-crystallin also possesses the enzymatic activity of malate dehydrogenase.     

Changes in lactate and malate dehydrogenase isoenzymes in salmonella under the effect of potassium dichloroisocyanurate

The method of enzyme-electrophoresis in agar gel according to Wieme (1959) was used for the study of lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) isoenzymes of 24-hour and 48-hour Salmonella cultures exposed to a 0.02% solution of potassium dichloroisocyanurate (PDIC). Severe repression of LDH and MDH isoenzymes was observed immediately after the exposure of the culture to the disinfectant solution. A significant decrease in the content of the isoenzyme LDH1 and of the cytoplasmic fraction (C1) of MDH simultaneously with the appearance of the fractions LDH4, LDH1a and LDH1b were established in the strains cultured on MPA in the course of 24 hours following the exposure. A tendency to a decrease in the LDH1 content was preserved in the experimental cultures after 48 hours, but the spectrum of MDH isoenzymes showed almost no differences in comparison with that of MDH isoenzymes in 48-hour cultures of the control strains.     

Activity patterns of phosphofructokinase,glyceraldehydephosphate dehydrogenase,lactate dehydrogenase and malate dehydrogenase in microdissected fast and slow fibres from rabbit psoas and soleus muscle

Summary Methods for standardized determination of phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in nanogram samples of microdissected single fibres of rabbit psoas and soleus muscle are described. Fast and slow fibres in soleus muscle show lower absolute activities of these enzymes than the respective fibre types in psoas muscle. Slow fibres represent a more uniform population in the two muscles according to absolute and relative activities of the enzymes investigated. Slow fibres are characterized by high activities of MDH and relatively low activities of glycolytic enzymes. Fast fibres in the soleus muscle represent a population with high activities of MDH and glycolytic enzymes. Fast fibres in psoas muscle represent a heterogeneous population with high activities of glycolytic enzymes and extremely variable activity of MDH. More than 10-fold differences exist in the MDH activities of the extreme types of this fibre population. Differences in the activity levels of MDH in single fast type fibres but also in the activities of glycolytic enzymes between fast and slow fibres are greater than those reported between extreme white and red rabbit muscles.     

Activity patterns of phosphofructokinase, glyceraldehydephosphate dehydrogenase, lactate dehydrogenase and malate dehydrogenase in microdissected fast and slow fibres from rabbit psoas and soleus muscle.

Methods for standardized determination of phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in nanogram samples of microdissected single fibres of rabbit psoas and soleus muscle are described. Fast and slow fibres in soleus muscle show lower absolute activities of these enzymes than the respective fibre types in psoas muscle. Slow fibres represent a more uniform population in the two muscles according to absolute and relative activities of the enzymes investigated. Slow fibres are characterized by high activities of MDH and relatively low activities of glycolytic enzymes. Fast fibres in the soleus muscle represent a population with high activities of MDH and glycolytic enzymes. Fast fibres in psoas muscle represent a heterogeneous population with high activities of glycolytic enzymes and extremely variable activity of MDH. More than 10-fold differences exist in the MDH activities of the extreme types of this fibre population. Differences in the activity levels of MDH in single fast type fibres but also in the activities of glycolytic enzymes between fast and slow fibres are greater than those reported between extreme white and red rabbit muscles.     

Changes in lactate dehydrogenase and malate dehydrogenase activities during hypoxia and after temperature acclimation in the armored fish, Rhinelepis strigosa (Siluriformes, Loricariidae)

Lactate (LDH) and malate dehydrogenase (MDH) of white skeletal muscle of fishes acclimated to 20, 25 and 30 degrees C and thereafter submitted to hypoxia were studied in different substrate concentrations. Significant differences for LDH and MDH of white muscle enzyme activities are described here for the first time in Rhinelepis strigosa of fishes acclimated to 20 degrees C and submitted to hypoxia for six hours. LDH presented a significant decrease in enzyme affinity for pyruvate in acute hypoxia, for fishes acclimated to 20 degrees C and an increase for fishes acclimated to 30 degrees C.     

The development of lactate and malate dehydrogenases in the C57BL-6 mouse kidney

The development of lactate dehydrogenase (LDH; EC 1.1.1.27) and malate dehydrogenase (MDH; EC 1.1.1.37) was measured in the kidney of male and female $\text{C57BL}\text{6}$ mice from ages prenatal 16 days to 80 days. Maximum reactions rates of the enzymes were measured in vitro by following the reduction of the nicotinamide-adenine dinucleotide spectrophotometrically.Analysis of variance showed no significant sex difference for LDH and MDH. There was a significant sex difference for the ratio LDH:MDH and a significant age difference for LDH, MDH, and the ratio LDH:MDH. In the male and female, LDH activity increased from prenatal 16 days to 30 days. Malate dehydrogenase activity reached adult values at 22 days in the male and at 30 days in the female. The ratio LDH:MDH in the male decreased from prenatal 16 days to 3 days, after which the ratio continued to decline to 20 days at a less rapid rate. This general pattern was also found in the female followed by a further decline in the ratio at 50 days.The development of LDH and MDH in the $\text{C57BL}\text{6}$ mouse is tissue specific and probably parallels the development of the tissue's function. In the case of the kidney, LDH and MDH development may reflect maturation of mitochondrial function and the kidney's ability to concentrate urine.     

Functions of the membrane-associated and cytoplasmic malate dehydrogenases in the citric acid cycle of Corynebacterium glutamicum

Like many other bacteria, Corynebacterium glutamicum possesses two types of L-malate dehydrogenase, a membrane-associated malate:quinone oxidoreductase (MQO; EC 1.1.99.16) and a cytoplasmic malate dehydrogenase (MDH; EC 1.1.1.37) The regulation of MDH and of the three membrane-associated dehydrogenases MQO, succinate dehydrogenase (SDH), and NADH dehydrogenase was investigated. MQO, MDH, and SDH activities are regulated coordinately in response to the carbon and energy source for growth. Compared to growth on glucose, these activities are increased during growth on lactate, pyruvate, or acetate, substrates which require high citric acid cycle activity to sustain growth. The simultaneous presence of high activities of both malate dehydrogenases is puzzling. MQO is the most important malate dehydrogenase in the physiology of C. glutamicum. A mutant with a site-directed deletion in the mqo gene does not grow on minimal medium. Growth can be partially restored in this mutant by addition of the vitamin nicotinamide. In contrast, a double mutant lacking MQO and MDH does not grow even in the presence of nicotinamide. Apparently, MDH is able to take over the function of MQO in an mqo mutant, but this requires the presence of nicotinamide in the growth medium. It is shown that addition of nicotinamide leads to a higher intracellular pyridine nucleotide concentration, which probably enables MDH to catalyze malate oxidation. Purified MDH from C. glutamicum catalyzes oxaloacetate reduction much more readily than malate oxidation at physiological pH. In a reconstituted system with isolated membranes and purified MDH, MQO and MDH catalyze the cyclic conversion of malate and oxaloacetate, leading to a net oxidation of NADH. Evidence is presented that this cyclic reaction also takes place in vivo. As yet, no phenotype of an mdh deletion alone was observed, which leaves a physiological function for MDH in C. glutamicum obscure.