Relationship of 3 alpha-hydroxysteroid dehydrogenase to pyridine nucleotide transhydrogenases

It appears that the alpha-hydroxysteroid dehydrogenases are not significant entities in promoting transhydrogenase reactions in animal tissues.     

A specific, highly active malate dehydrogenase by redesign of a lactate dehydrogenase framework

Three variations to the structure of the nicotinamide adenine dinucleotide (NAD)-dependent L-lactate dehydrogenase from Bacillus stearothermophilus were made to try to change the substrate specificity from lactate to malate: Asp197----Asn, Thr246----Gly, and Gln102----Arg). Each modification shifts the specificity from lactate to malate, although only the last (Gln102----Arg) provides an effective and highly specific catalyst for the new substrate. This synthetic enzyme has a ratio of catalytic rate (kcat) to Michaelis constant (Km) for oxaloacetate of 4.2 x 10(6)M-1 s-1, equal to that of native lactate dehydrogenase for its natural substrate, pyruvate, and a maximum velocity (250 s-1), which is double that reported for a natural malate dehydrogenase from B. stearothermophilus.     

Pregnancy suppression by an antiserum to the sperm specific lactate dehydrogenase

An antiserum induced against the isozyme of lactate dehydrogenase (LDH-X) that is unique to spermatozoa reduced significantly the number of pregnancies in mice treated at varying times after they had mated. This effect of the antiserum occurred both prior to and following implantation. The fecundity of treated animals appeared to be normal in subsequent matings.     

Polymorphism of lactate dehydrogenase in gelada baboons

In a group of 21 gelada baboons, three different lactate dehydrogenase patterns were observed after starch-gel electrophoresis of tissue extracts. The patterns indicate that a mutation has occurred in this population in the gene responsible for the A-subunit. The normal and variant homozygotes each contain five isozymes, those containing the A subunit having characteristically different electrophoretic mobilities. The heterozygote contains the expected 15 isozymes.     

Molecular size of hagfish muscle lactate dehydrogenase

In contrast to an earlier report, we find that the primitive vertebrate Eptatretus possesses a muscle lactate dehydrogenase whose molecular size is like that of lactate dehydrogenases from higher vertebrates. The molecular size of lactate dehydrogenase appears to have remained constant during evolution.     

Circadian rhythms in neurospora: spatial differences in pyridine nucleotide levels

A growing colony of a mutant strain of Neurospora crassa had two morphologically distinct areas which were formed as a result of a rhythmic spore-forming (conidiation) process. The total pyridine nucleotide content of these two areas was the same, but the levels of NADH, NADPH, and NADP were lower in the conidiating area, while the NAD level was higher. These biochemical differences in the adjacent areas of a single colony were only found in newly formed areas, and were not a permanent record. It is not known whether these pyridine nucleotide changes are a result of the conidiation process, or whether they are tied more directly to some underlying metabolic oscillation. However, it is speculated that the changes in the levels of these key coenzymes could have far-reaching effects on many areas of metabolism.     

Infertility in female rabbits immunized with lactate dehydrogenase X

Immunization of female rabbits with the sperm-specific lactate dehydrogenase (LDH-X) resulted in a highly significant reduction of pregnancies compared to nonimmunized controls. This is the first demonstration of immunosuppression of fertility by a crystalline protein shown to be strictly homogeneous by ultracentrifugation, polyacrylamide gel electrophoresis, immunodiffusion, and micro complement fixation.     

Genetic control of lactate dehydrogenase expression in mammalian tissues

The amount of lactate dehydrogenase isozyme 4 in erythrocytes of mice is controlled by alleles at the Ldr-1 locus. The A subunits of lactate dehydrogenase from erythrocytes deficient in isozyme 4 cannot assemble in vitro with B subunits to form active isozyme. The inability to form hybrid enzyme is not due to a mutation in the structural gene for the A polypeptide. Rather, a factor that is bound to the A subunits of erythrocytes restricts free exchange with B subunits.     

Peafowl lactate dehydrogenase: problem of isoenzyme identification

Peafowl, like other vertebrates, contain multiple forms of lactate dehydrogenase. The electrophoretic properties of the peafowl isoenzymes are unusual in that the isoenzyme from heart tissue can be either more or less anodic than that of muscle, depending on the pH. This finding focuses attention on the problem of isoenzyme identification. It is suggested that isoenzymes be identified on the basis of properties that are chemically and biologically more significant than electrophoretic mobility.     

四种黄颡鱼乳酸脱氢酶同工酶电泳的研究

黄颡鱼(Pelteabagrus)又名“黄姑子”、黄腊丁、黄鼓鱼等,在湖南,被称为“黄鸭叫”,隶属于鲶形目科,为广布性鱼类,在我国各大水系均有分布,特别是在长江中下游的湖泊更为集中。黄颡鱼喜栖息于水底层,夜间则游至水上层觅食。其肉质细嫩、味道鲜美,已逐渐成为一特种淡水养殖鱼类,其养殖规模有迅速扩大之势。有关黄颡鱼的研究较多,但主要仅集中于生态研究[1-4],发育研究[5,6]和疾病的防治[7-10]等,对黄颡鱼生理生化、亲缘关系等的研究所见报道极少[11]。鱼类同工酶差异是鱼种间不同生化遗传结构的反映,因此我们对分布于洞庭湖区四种黄颡…     

Linkage of lactate dehydrogenase B and C loci in pigeons

Synthesis of lactate dehydrogenase in somatic and gametic tissues of certain avian and mammalian species is controlled by alleles at three loci, A, B, and C. We report breeding experiments with pigeons that conclusively demonstrate linkage between the B and C structural loci in this species. The most probable recombination fraction is zero, and contiguity is not excluded. The upper 95 percent probability limit is 4.5 percent. This tight linkage of two loci that produce closely similar polypeptides suggests that the loci acquired their separate identities through a duplication event. Further-more, the existence of recognizable B- and C-type polypeptides in both the bird and the mammal suggests that the event and the resulting linkage preceded the separation of these fauna. If so, then the linkage has persisted for a very long time.     

Cytochemical localization of lactate dehydrogenase in muscular dystrophy of the mouse

By use of phenazine methosulfate and the "ncubation mixture film method," lactate dehydrogenase activity has been demonstrated in the dystrophic muscle fibers of strain 129 mice. The results indicate that for demonstration of lactate dehydrogenase activity in dystrophic muscle fibers phenazine methosulfate is necessary. This finding is typical for the "white" muscle fibers in the normal muscle and suggests that the dystrophy affects primarily the "white" muscle fibers.     

Genetic control of lactate dehydrogenase formation in the hagfish Eptatretus stoutii

The isozyme patterns of lactate dehydrogenases of various tissues were studied on 51 hagfish by starch-gel electrophoresis. Nine lactate dehydrogenase phenotypes were encountered, suggesting the coexistence of two alleles at each of the two separate gene loci. There apparently was no interaction between the products of these two separate loci. Even the products of two alleles at the same locus were apparently incapable of forming hybrid molecules, an indication of the possible monomeric nature of each lactate dehydrogenase molecule.     

Rabbit lactate dehydrogenase isozymes: effect of pH on activity

The ability of lactate dehydrogenase isozyme five from rabbit skeletal muscle to catalyze pyruvate reduction is extremely sensitive to changes of pH within the range of 6.2 to 7.8.The activity of lactate dehydrogenase isozyme one from rabbit heart is virtually unaffected by changes of pH within the same range. Isozyme five is activated by low concentrations of oxalacetate and inhibited by higher concentrations, but other substrates of the citric acid cycle have no effect.     

堆型艾美耳球虫乳酸脱氢酶基因的克隆与表达

克隆了堆型艾美耳球虫(Eimeria acervulina)乳酸脱氢酶(LDH)基因(EaLDH),并在大肠杆菌中成功表达出重组蛋白.根据GenBank中收录的EaLDH核苷酸序列设计特异性引物,以其第一代裂殖体总RNA为模板,采用RT-PCR方法扩增获得EaLDH基因.将EaLDH基因片段与原核表达载体pET28a(+)连接,构建重组表达质粒pET28a(+)-LDH,并在大肠杆菌BL21(DE3)中诱导表达.结果表明,扩增出的EaLDH基因含993 bP的开放阅读框,与GenBank中收录的EaLDH基因序列相似性为98%.诱导后,重组蛋白能够在大肠杆菌中高效表达,融合蛋白相对分子质量约为4.1×104.     

Constitution, viability, and lactate dehydrogenase in stationary-phase L-cell suspension cultures

Starved suspension cultures of L cells exhibit a plateau phase of short duration followed by loss of key cellular constituents and rapidly decreasing viability. In contrast, regularly fed,. undiluted cultures remain stationary at a high cell density for prolonged periods without structural alterations or loss of viability. The L cells contain a single lactate dehydrogenase isozyme with an electrophoretic mobility similar to that of lactate-dehydrogenase-5. High-density stationary cultures show a tenfold increase of the specific activity of this enzyme and a recurrent biphasic pattern of carbohydrate utilization with, first, production and, later, consumption of lactate.     

Horseshoe crab lactate dehydrogenase: tissue distribution and molecular weight

Lactate dehydrogenase from Xiphosura (Limulus) polyphemus i D(-)-lactate specific. It does not use L(+)-lactate, alpha-hydroxybutyrate, alpha-hydroxyvalerate, or alpha-hydroxyisocaproate as substrate. In most tissues lactate dehydrogenase is composed of five isozymes with a molecular weight of 140,000 for each, as judged by gel-filtration chromatography. This suggests that the isozyme, are tetramers comprised of varying amounts of two physicochemically distinc subunits.