Identification and characterization of a hypoxically induced maize lactate dehydrogenase gene

In cereal root tissue, hypoxia induces the enzyme lactate dehydrogenase (LDH); (S)-lactate:NADH oxidoreductase, EC 1.1.1.27). In barley, both biochemical and genetic data indicate that five isozymes are induced under hypoxia. These isozymes are tetramers and arise from the random association of the products of two Ldh genes. The induction of LDH activity in root tissue has been shown to be correlated to an increase in LDH protein and Ldh mRNA.In order to more fully characterize the hypoxic induction of LDH, we have isolated a maize Ldh genemic clone which has strong homology at both the amino acid and nucleotide level to the barley LDH cDNA clones. The Ldh1 gene consists of two exons separated by a 296 bp intron, has the expected eukaryotic regulatory signals and a sequence that has strong homology to the maize anaerobic regulatory element.     

Evolutionary evidence for a regulator gene controlling the lactate dehydrogenase B gene in rodent erythrocytes

Erythrocyte and tissue lactate dehydrogenase (LDH) electrophoretic patterns of 26 rodent species from ten families were examined. The LDH B gene was observed to range in erythrocyte expression from species without detectable B subunits to those which predominantly expressed B subunits. However, the shift in erythrocyte B gene expression was not observed in the tissue LDH electrophoretic patterns between rodent species. Species which did not express erythrocyte B subunits, or only small quantities of B subunits, were restricted to the suborder Myomorpha. In erythrocytes of other rodent species, and most mammals, LDH B subunits are expressed equally or in excess of A subunits. The results suggest either structural differences in the LDH B gene between Myomorph and non-Myomorph rodents or a regulator gene which controls the expression of the B gene in Myomorph erythrocytes. Existing evidence favors the latter hypothesis.Supported by U.S. Public Health Service Grants 5F2 HD-35,531 (T.B.S.), GM-09966 (F.H.R.), G.R.S. 5 SO1 FR-05400-07, and NSF GB 5440X (E.J.M.).     

Detection of lactate dehydrogenase B4 in human hemolysate of patients deficient in lactate dehydrogenase B subunit activity using enzyme immunoassay

We developed a sensitive enzyme immunoassay system specific for human lactate dehydrogenase (LDH)- B₄ with antiacetylated LDH-B₄ Fab-horse-radish peroxidase conjugate. The enzyme immunoassay system was not interfered with by up to 0.3 mg/tube of hemoglobin. Thus, we measured LDH-B₄ concentrations in the hemolysate of seven heterozygous individuals deficient in LDH-B subunit activity and eight normal individuals. We could not find a significant difference between the LDH-B₄ concentrations in heterozygous and those in normal individuals. These results demonstrate that heterozygous individuals deficient in LDH-B subunit activity produce enzymatically inactive B subunits.This work was supported in part by grants in aid for Scientific Research from the Ministry of Education, Japan (59570998), and from the Clinical Pathology Research Foundation of Japan.     

Discovery of gene families and alternatively spliced variants by RecA-mediated cloning

Probing the functional complexity of the human genome will require new gene cloning techniques, not only to discover intraspecies gene homologs and interspecies gene orthologs, but also to identify alternatively spliced gene variants. We report homologous cDNA cloning methods that allow cloning of gene family members, genes from different species, and alternatively spliced gene variants. We cloned human 14-3-3 gene family members using DNA probes with as much as 35% sequence divergence, cloned alternatively spliced gene forms of Rad51D, and cloned a novel splice form of the human 14-3-3 theta gene with a unique expression pattern. Interspecies gene cloning was demonstrated for the mouse Rad51C and mouse beta-actin genes using human gene probes. The gene family cloning method is fast, efficient, and free from PCR errors; moreover, it exploits the abilities of RecA protein to pair homologous or partially homologous DNA sequences stably in kinetically trapped, multistranded DNA hybrids that can be used for subsequent gene clone enrichment.     

Phosphorylation of lactate dehydrogenase by ATP

Evidence is presented indicating that phosphorylation of porcine muscle lactate dehydrogenase by [gamma-32P] ATP occurs at carboxyl residues of the protein. The phosphoenzyme complex was moderately stable at pH 6.8 and 25 degrees C, with a half-life of 3.5 h. In the presence of NADH rapid dephosphorylation occurred. Formation of an abortive complex with NAD-pyruvate also caused hydrolysis of the phosphoenzyme. The phosphorylated lactate dehydrogenase was shown to serve as a phosphate donor for phosphorylation of ADP.     

Two erythrocytic lactate dehydrogenase variants in the house mouse, Mus musculus

Two erythrocytic LDH variants have been found in the house mouse, Mus musculus. One, involving the presence and absence of the next to the slowest electrophoretically separable isozyme, is controlled by a regulatory locus which may be similar to Ldr-1 (Shows and Ruddle, 1968). The second appears to be indirectly controlled by the Hbb locus and may be attributed to the accumulation of a storage product in the lysates. Ldr-1 is polymorphic in natural populations of the house mouse.     

Identification and characterization of yak (Bos grunniens) b-Boule gene and its alternative splice variants

Boule is responsible for meiotic arrest of sperms and male sterility during mammalian spermatogenesis. In the present study, we first identified yak b-Boule gene and its two alternative splice variants. The full length coding region of yak b-Boule is 888 bp and encodes a 295-amino acid protein with a typical RNA-recognition motif (RRM) and a Deleted in Azoospermia (DAZ) repetitive sequence motif. Two alternative splice variants of yak b-Boule were generated following the consensus “GT-AG” rule and named b-Boule1 (36 bp deletion in exon 3) and b-Boule2 (deletion of integral exon 7), respectively. In male yak, b-Boule, b-Boule1 and b-Boule2 were found to be exclusively expressed in the testes at a ratio of 81:0.1:1. Intriguingly, the mRNA expression levels of b-Boule and b-Boule1 in yak testis were significantly higher than those in cattle–yak, although no significant difference was observed for b-Boule2 expression between the yak and cattle–yak. These results suggest that b-Boule gene, which is partially regulated by alternative splicing, may be involved in the process of yak spermatogenesis.     

Evolution of Cryptosporidium parvum lactate dehydrogenase from malate dehydrogenase by a very recent event of gene duplication

We have expressed the L-lactate dehydrogenase (LDH) and L-malate dehydrogenase (malDH) genes from the apicomplexan Cryptosporidium parvum (CpLDH1 and CpMalDH1) as maltose-binding protein (MBP) fusion proteins in Escherichia coli. The substrate specificities, enzymatic kinetics, and oligomeric states of these two parasite enzymes have been characterized. By taking advantage of recently completed and ongoing apicomplexan genome sequencing projects, we identified additional MalDH genes from Plasmodium spp., Toxoplasma gondii, and Eimeria tenella that were previously unavailable. All apicomplexan MalDHs appeared to be cytosolic and no organellar homologs were identified from the completely sequenced P. falciparum genome and other ongoing apicomplexan genome-sequencing projects. Using these expanded apicomplexan LDH and MalDH sequence databases, we reexamined their phylogenetic relationships and reconfirmed their relationship to alpha-proteobacterial MalDHs. All LDH and MalDH enzymes from apicomplexans were monophyletic within the LDH-like MalDH group (i.e., MalDH resembling LDH) as a sister to alpha-proteobacterial MalDHs. All apicomplexan LDHs, with the exception of CpLDH1, formed a separate clade from their MalDH counterparts, indicating that these LDHs were evolved from an ancestral apicomplexan MalDH by a gene duplication coupled with functional conversion before the expansion of apicomplexans. Finally, CpLDH1 was consistently placed together with CpMalDH1 within the apicomplexan MalDH cluster, confirming an early working hypothesis that CpLDH1 was probably evolved from the same ancestor of CpMalDH1 by a very recent gene duplication that occurred after C. parvum diverged from other apicomplexans.     

Cloning of a lactate dehydrogenase gene from Clostridium acetobutylicum B643 and expression in Escherichia coli

A lactate dehydrogenase (LDH) gene of Clostridium acetobutylicum B643 was cloned on two recombinant plasmids, pPC37 and pPC58, that were selected by complementation of Escherichia coli PRC436 (acd), a fermentation-defective mutant that does not grow anaerobically on glucose. E. coli PRC436(pPC37) and PRC436(pPC58) grew anaerobically and fermented glucose to mostly lactate. When pPC37 and pPC58 were transformed into E. coli FMJ39 (ldh pfl), an LDH-deficient strain, the resulting strains grew anaerobically on glucose and produced lactate. Crude extracts of E. coli FMJ39(pPC37) and FMJ39(pP58) contained high LDH activity only when assayed for pyruvate reduction to lactate, and the LDH activity was activated 15- to 30-fold by the addition of fructose 1,6-diphosphate (FDP). E. coli FMJ39 had no detectable LDH activity, and E. coli LDH from a wild-type strain was not activated by FDP. Maxicell analysis showed that both plasmids pPC37 and pPC58 expressed a protein with an apparent Mr of 38,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Restriction endonuclease mapping of pPC37 and pPC58 and DNA hybridization studies indicated that a 2.1-kb region of these two clones of C. acetobutylicum DNA encodes the FDP-activated LDH.     

The cDNA cloning and molecular evolution of reptile and pigeon lactate dehydrogenase isozymes

The cDNAs encoding lactate dehydrogenase isozymes LDH-A (muscle) and LDH-B (heart) from alligator and turtle and LDH-A, LDH-B, and LDH-C (testis) from pigeon were cloned and sequenced. The evolutionary relationships among vertebrate LDH isozymes were analyzed. Contrary to the traditional belief that the turtle lineage branched off before the divergence between the lizard/alligator and bird lineages, the turtle lineage was found to be clustered with either the alligator lineage or the alligator-bird clade, while the lizard lineage was found to have branched off before the divergence between the alligator/turtle and bird lineages. The pigeon testicular LDH-C isozyme was evidently duplicated from LDH-B (heart), so it is not orthologous to the mammalian testicular LDH-C isozymes.      

Identification of 3,6-disubstituted dihydropyrones as inhibitors of human lactate dehydrogenase

A series of 3,6-disubstituted dihydropyrones were identified as inhibitors of human lactate dehydrogenase (LDH)-A. Structure activity relationships were explored and a series of 6,6-spiro analogs led to improvements in LDHA potency (IC₅₀ <350 nM). An X-ray crystal structure of an improved compound bound to human LDHA was obtained and it illustrated additional opportunities to enhance the potency of these compounds, resulting in the identification of 51 (IC₅₀ = 30 nM).     

Refolding of lactate dehydrogenase by zeolite beta

We used zeolite beta as an adsorbing matrix to refold recombinant lactate dehydrogenase (LDH) protein collected as an insoluble aggregate from a bacterial expression system. The adsorption isotherm revealed that 1 g of zeolite adsorbed 200 mg of denatured LDH solubilized with a buffer containing 6 M of guanidine hydrochloride. The pH of the buffer had little effect on the adsorption, but this property was abolished by preincubation of the zeolite with polyethylene glycol (PEG) in a weight ratio of 1:10. These data suggest that the adsorption of LDH depends on the hydrophobicity of the zeolite surface, and that the adsorption of PEG to zeolite is sufficient to release LDH from its surface. LDH was thus released by refolding buffer containing PEG and arginine, and soluble LDH was obtained in its active enzymatic form. The addition of arginine dramatically increased the yield of LDH in a dose‐dependent manner. The overall refolding efficiency was optimized to 35%. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

The disproportionation of glyoxylate by lactate dehydrogenase

Lactate dehydrogenase (EC 1.1.1.27) catalyzes the NAD-dependent oxidation to (oxalate) and reduction (to glycollate) of glyoxylate. The kinetics of this disproportionation are in accord with the usual reaction pathway of lactate dehydrogenase:substrate inhibition with appropriate pH dependence occurs; a steady state in the ratio of NADH to NAD⁺ is set up during the reaction, has the expected dependence on pH, and is independent of the initial glyoxylate, coenzyme, and enzyme concentration. At pH 7 the lactate dehydrogenase-NADH complex is about fivefold more likely to react with and reduce glyoxylate (at a concentration of 100 mm) than to dissociate to produce free NADH, and the ratio of the fraction of the enzyme-NADH complex which dissociates to the fraction which reacts with and reduces glyoxylate varies with glyoxylate concentration and with pH in a manner in agreement with the normal reaction pathway of the enzyme. With all concentrations of glyoxylate and over the pH range 7–9.6 both free (not enzyme bound) NAD⁺ and free NADH are formed in the steady state of the disproportionation. From these results it is apparent that lactate dehydrogenase, like alcohol dehydrogenase (EC 1.1.1.1), catalyzes a disproportionation within the bounds of its normal kinetic reaction pathway.     

Phosphorylation of lactate dehydrogenase by protein kinases

The influence of phosphorylation on the properties of lactate dehydrogenase (LDH) has been studied. Data obtained using the immobilization approach support the assumption that the autophosphorylation of LDH discovered previously in the presence of ATP has no relation to protein kinase activity of the enzyme. Phosphorylation of native LDH by tyrosine kinases was shown to be inefficient. However, the efficiency of the phosphorylation considerably increased after the dissociation of LDH into non-native forms of the enzyme. Ca2+/calmodulin-dependent protein kinase catalyzes incorporation of 0.8-0.9 mole phosphate per mole of LDH tetramer. The phosphorylation results in an increase in activity by 25-30% and increases markedly the stability of the enzyme during cold inactivation. Phosphorylation of LDH by Ca2+/calmodulin-dependent protein kinase, unlike the phosphorylation on tyrosine residues, is supposed to be of importance for the control of cell metabolism.     

Estimation of the gene frequency of lactate dehydrogenase subunit deficiencies

To detect the frequency of lactate dehydrogenase (LDH) subunit deficiency, screening for LDH subunit deficiency was performed on 3,776 blood samples from healthy individuals in Shizuoka Prefecture by means of electrophoresis. The frequency of heterozygote with LDH-A subunit deficiency was found to be 0.185%, and with LDH-B subunit deficiency, 0.159%. The frequencies of both subunit deficiencies were not significantly different. Gene frequencies of LDH subunit deficiencies were calculated by the simple counting procedure, and the results are as follows: gene frequency of LDH-A subunit deficiency was 11.9 X 10(-4), and that of LDH-B subunit deficiency, 7.9 X 10(-4). In addition, the second case in the world of a homozygous individual with LDH-A subunit deficiency was detected by this screening. This case with regard to the characteristics of LDH-A subunit deficiency are summarized herein.