Forms Of Lactate Dehydrogenase Research Articles

The kinetic properties and sensitivities to inhibitors of lactate dehydrogenases (LDH1 and LDH2) from Toxoplasma gondii: comparisons with pLDH from Plasmodium falciparum

Toxoplasma gondii differentially expresses two forms of lactate dehydrogenase in tachyzoites and bradyzoites, respectively, designated LDH1 and LDH2. Previously it was demonstrated that LDH1 and LDH2 share a unique structural feature with LDH from the malarial parasite Plasmodium falciparum (pLDH), namely, the addition of a five-amino acid insert into the substrate specificity loops. pLDH exhibits a number of kinetic properties that previously were thought to be unique to pLDH. In the present study, kinetic properties of LDH1 and LDH2 were compared with those of pLDH. LDH1 and LDH2 exhibit broader substrate specificity than pLDH. For both LDH1 and LDH2, 3-phenylpyruvate is an excellent substrate. For LDH2, 3-phenylpyruvate is a better substrate even than pyruvate. By comparison, pLDH does not utilize 3-phenylpyruvate. Both LDH1 and LDH2 can utilize the NAD analog 3-acetylpyridine adenine dinucleotide (APAD) efficiently, similar to pLDH. LDH1 and LDH2 are inhibited competitively by a range of compounds that also inhibit pLDH, including gossypol and derivatives, dihydroxynaphthoic acids, and N-substituted oxamic acids. The lack of substrate inhibition observed with pLDH is also observed with LDH2. By comparison, LDH1 differs from LDH2 in exhibiting substrate inhibition in spite of an identical residue (M163) at a cofactor binding site that is thought to be critical for production of substrate inhibition. For gossypol and gossylic iminolactone, but not the other gossypol derivatives tested, the in vitro inhibition of T. gondii LDH activity correlated with specific inhibition of T. gondii tachyzoite growth in fibroblast cultures.

Enzyme typing of southern African isolates of Plasmodium falciparum by polyacrylamide gel electrophoresis

Nineteen southern African isolates of Plasmodium falciparum were typed by polyacrylamide gel electrophoresis, using 5 enzymes (glucose phosphate isomerase, adenosine deaminase, lactate dehydrogenase, NADP-dependent glutamate dehydrogenase and 6-phosphogluconate dehydrogenase). Limited variation was found amongst the isolates and the frequencies of variants were similar to those of isolates from other parts of the world. Eight of the isolates contained 2 forms of glucose phosphate isomerase, indicating clonal heterogeneity. One of these 8 isolates also contained 2 forms of adenosine deaminase and another showed 2 forms of lactate dehydrogenase.

Protein carboxyl methyltransferase facilitates conversion of atypical L-isoaspartyl peptides to normal L-aspartyl peptides.

Prolonged incubation of L-isoaspartate-containing forms of lactate dehydrogenase (231-242), sperm activating peptide, and adrenocorticotropin (22-27) at 37 degrees C, pH 7.4, with S-adenosyl-L-methionine and protein carboxyl methyltransferase from bovine brain leads to extensive conversion of the atypical isopeptide bond to a normal peptide bond. For the lactate dehydrogenase-related peptide, conversion was 80% complete after 24 h. For the other two peptides, conversion reached a level of approximately 65% after 48 h. The mechanism of conversion involves (i) rapid enzymatic methylation of the alpha-carboxyl of the L-iso-Asp residue; (ii) nonenzymatic demethylation resulting in formation of an L-aspartyl cyclic imide; and (iii) a slow, nonenzymatic hydrolysis of the cyclic imide to form a mixture of 15-25% normal L-Asp peptide and 75-85% L-iso-Asp peptide. The regenerated L-iso-Asp peptide is remethylated and the cycle is repeated. The extent of conversion is limited by a competing side reaction wherein the L-imide slowly racemizes, leading to the formation of mainly D-iso-Asp peptide, which is not a substrate for the methyltransferase. The ability of protein carboxyl methyltransferase to initiate conversion of L-iso-Asp residues to normal L-Asp suggests a possible role for this enzyme in facilitating the repair or degradation of deamidated proteins in vivo.

Separation of rat lactate dehydrogenase isoenzyme C4 from other isoenzymes by affinity and ion-exchange chromatography

Lactate dehydrogenase C, an isoenzyme composed of C polypeptide subunits and found only in mature testes and spermatozoa, differs kinetically, chemically and immunologically from the five common isoenzymes of lactate dehydrogenase, each of which is a tetramer of A and/or B subunits. In the rat lactate dehydrogenase C exists in two molecular forms, isoenzymes C4 and A1C3. In addition to these two forms of lactate dehydrogenase C, rat testicular homogenate contains all the five isoenzymes of A and B type. Purification of isoenzyme C4 requires its separation from the other six isoenzymes, of which isoenzymes A1C3 and A3B1 are the most difficult ones to separate. In the present study isoenzyme A3B1, along with other enzymes, was separated from isoenzyme C4 by AMP-Sepharose chromatography by using a gradient of increasing concentration of NAD+-pyruvate adduct. In the next step, isoenzyme A1C3 was separated from isoenzyme C4 by DEAD-cellulose chromatography, resulting in a pure lactate dehydrogenase isoenzyme C4 preparation.

Effect of audiogenic seizures on activity of H and M forms of lactate dehydrogenase in neurons and neuroglia in various parts of the central nervous system

Cytospectrophotometric analysis showed that the ratio between activities of aerobic H forms of lactate dehydrogenase (LD) and the activity of its anaerobic M forms in cerebral cortical neurons and cerebellar Purkinje cells and also in their glial satellite cells of rats of the Krushinskii-Molodkina and Wistar strains is higher than in motoneurons in the anterior horns of the spinal cord and their perineuronal glia. In Krushinskii-Molodkina rats (with genetically determined high sensitivity to audiogenic seizures) epileptiform audiogenic seizures were accompanied by marked activation of both H and M forms of LD in the cortical neurons but by absence of changes in the perineuronal glia. In the spinal motoneurons, on the other hand, the activity of all forms of LD was unchanged, whereas in the neuroglial cells surrounding these neurons activity of the H forms of LD was definitely increased. During the seizures an increase in activity of M forms of LD was found in the cerebellar Purkinje cells but a decrease in their activity in the glial satellite cells.

Lactate Dehydrogenases of the Treefrog Hyla regilla: Subunit Homologies and Genetic Variation

Five major forms of lactate dehydrogenase were detected in most specimens of Hyla regilla examined by electrophoresis. They were designated M4, MaH, M2H2, MH3 and H4 on the basis of electrophoretic migration, thermal stability, immunological properties, tissue distribution and catalytic properties. An electrophoretic search for allelic variation at the loci coding for the M and H subunits was made with extracts prepared by soaking toes in a phenoxyethanol solution. A total of 414 individuals, representing 4 subspecies and 9 populations, from Oregon and California were screened. The search revealed 10 presumptively heterozygous individuals: 4 at the Ldh-M locus, 5 at the Ldh-H locus and one at both loci. As the presumptive heterozygotes appeared to produce approximately equal amounts of the variant and wild-type subunits, each locus was judged to be single (rather than duplicate).

A crystalline form of testes-specific lactate dehydrogenase

A preliminary X-ray diffraction examination of crystals of lactate dehydrogenase from mouse testes (LDH-X) showed these to be triclinic. The one molecule per unit cell occupies a similar crystal volume to other forms of lactate dehydrogenase.

Multiple forms of lactate dehydrogenase in the cod, Gadus morhua L.

Five types of subunits are postulated to explain the lactate dehydrogenase zymogram patterns of cod tissues. The subunits designated A, B, and C occur predominantly in white skeletal muscle, heart, and liver tissues, respectively. The D subunit is found almost exclusively in the retina. Activity of the E subunit is found in most tissues but does not appear to be predominant in any one tissue. The A subunits are most susceptible to heat treatment. The B subunits are the least reactive when AcPyAD, an NAD analogue, is used in place of NAD. Subbands may be produced in incubating heart or muscle extracts with pyloric caeca extract or with trypsin or chymotrypsin. Subbands normally appearing in tissues zymograms may represent partially synthesized or partially degraded active LDH tetramers normally present in a metabolizing tissue. In a sampling of three Canadian and one European cod populations, four forms of the heart subunit were found. They are designated B, B′, B″, and B‴. Allele frequencies of the heart types for each population sample are compared.

Inhibition of Catalase and Lactate Dehydrogenase by Radiation-Protective Thiols and Thiol Derivatives

A series of amino and guanidino thiols and thiol derivatives has shown a parallelism between their radiation-protective abilities in mice and their ability to inhibit the metalloenzyme catalase. Exceptions were found with a dithiocarbamate, which has higher metal-binding strength than the thiols, and a thiosulfate, which has weaker metal-binding ability. Inhibition of two forms of lactate dehydrogenase, where metal binding is unlikely, showed no correlation with radiation protection. This suggests that protection of catalase from radiation damage by agents that complex with the iron constituent constitutes one means of protecting animal cells from radiation-produced peroxides.

Lactate Dehydrogenase of Trout: Hybridization in vivo and in vitro

Speckled trout and lake trout contain five forms of lactate dehydrogenase, but a diflerent electrophoretic distribution of isozymes characterizes each species. The hybrid splake, which is produced artificially by fertilizing lake trout eggs with speckled trout sperm, contains nine isozymes. This comnplement of isozymeg In vivo could be produced in vitro by recombination of subunits from tissues of the parent species. In the splake trout, this complement is the result of heterozygosity at the gene locus responsible for synthesis of LDH-5. Extracts of trout eyes contain at least two additional forms of LDH which could not be demonstrated in other tissues.

LACTATE DEHYDROGENASES IN TROUT: EVIDENCE FOR A THIRD SUBUNIT.

Various tissues of the brook trout contain as many as nine forms of lactate dehydrogenase, an indication that at least three polypeptide subunits synthesized under the control of three nonallelic genes take part in the lactate dehydrogenase composition of this species. There was no evidence of a spermatozoan-specific lactate dehydrogenase.