Lactate dehydrogenase isozymes of testis and sperm: biological and biochemical properties and genetic control

What sperm can teach us about energy production

Mammalian sperm have evolved under strict selection pressures that have resulted in a highly polarized and efficient design. A critical component of that design is the compartmentalization of specific metabolic pathways to specific regions of the cell. Although the restricted localization of mitochondria to the midpiece is the best known example of this design, the organization of the enzymes of glycolysis along the fibrous sheath is the primary focus of this review. Evolution of variants of these metabolic enzymes has allowed them to function when tethered, enabling localized energy production that is essential for sperm motility. We close by exploring how this design might be mimicked to provide an energy-producing platform technology for applications in nanobiotechnology.

Sequential reactions of surface- tethered glycolytic enzymes

The development of complex hybrid organic-inorganic devices faces several challenges, including how they can generate energy. Cells face similar challenges regarding local energy production. Mammalian sperm solve this problem by generating ATP down the flagellar principal piece by means of glycolytic enzymes, several of which are tethered to a cytoskeletal support via germ-cell-specific targeting domains. Inspired by this design, we have produced recombinant hexokinase type 1 and glucose-6-phosphate isomerase capable of oriented immobilization on a nickel-nitrilotriacetic acid modified surface. Specific activities of enzymes tethered via this strategy were substantially higher than when randomly adsorbed. Furthermore, these enzymes showed sequential activities when tethered onto the same surface. This is the first demonstration of surface-tethered pathway components showing sequential enzymatic activities, and it provides a first step toward reconstitution of glycolysis on engineered hybrid devices.

Lactate dehydrogenase from the northern krill Meganyctiphanes norvegica: comparison with LDH from the Antarctic krill Euphausia superba

Electrophoretic polymorphism of lactate dehydrogenase (LDH, EC 1.1.1.27) from abdominal muscle is reported in the northern krill Meganyctiphanes norvegica. In the population, from the Gullmarsfjord (west coast of Sweden), LDH was encoded for by two different Ldh-A* and -B* loci. The isoenzymes were named according to their electrophoretic mobilities. Ldh-A* locus was polymorphic. The allelic frequencies were a=0.99, a'=0.002, a"=0.004, a"'=0.004. The level of LDH polymorphism is low. Most individuals possess the same amount of two LDH homopolymers (LDH-A*(4) and LDH-B*(4)). The Meganyctiphanes norvegica LDH-A*(4) and LDH-B*(4) isoenzymes and the predominant LDH-A*(4) isoenzyme from Euphausia superba were purified to specific activities of 294, 306 and 464 micromol NADH min(-1) mg(-1), respectively. In both species the LDH isoenzymes were separated by chromatofocusing. All three isoenzymes are L-specific tetramers with molecular weight of approximately 160 kDa. Northern krill LDH-A*(4) has higher affinity for pyruvate and lactate and is more thermostable than LDH-B*(4). Both isoenzymes are inhibited significantly by high concentration of pyruvate but not lactate. Antarctic krill isoenzyme exhibits high substrate affinities, high NAD inhibition, high inhibition at 10 mM pyruvate, lack of lactate inhibition, and high heat stability and resembles northern krill LDH-A*(4) isoenzyme.

Mouse lactate dehydrogenase (LDH) C4 (testis) is immunochemically cross-reactive with LDH A4 (muscle) and LDHB4 (heart)

It has been reported that lactate dehydrogenase (LDH) purified from testes (LDH C) of homotherms is not immunochemically cross-reactive with somatic forms of LDH purified from heart (LDH B) or muscle (LDH A). On the basis of this premise, LDH C has been considered for use as a contraceptive vaccine. Data presented here indicate that mouse antisera to either mouse or rat LDH C are cross-reactive with LDH A and B purified from muscle and heart tissues of mice. However, rabbit antisera to mouse LDH C are not cross-reactive with either mouse LDH A or B. Thus, the degree of cross-reactivity is dependent on the species from which the immunogen LDH is purified, the antisera are derived, and the LDH used in the assay is purified. The determination that LDH A, B, and C are immunochemically cross-reactive is of importance in evaluating LDH C as an immunogen in an immunologic approach to contraception.

Structural relatedness of mouse lactate dehydrogenase isozymes, A4 (muscle), B4 (heart), and C4 (testis)

Three homotetrameric lactate dehydrogenase isozymes, LDH-M(A4), LDH-H(B4), and LDH-X(C4), from DBA/2J mice have been purified by affinity chromatography. The amino acid compositions of the subunits A,B, and C, based on a molecular weight of 36,000, have been determined. The compositional relatedness of these isozymes indicates that subunits A (muscle) and B (heart) are more closely related to each other than to subunit C (testis). Tryptic peptide maps and amino acid compositions of some active site peptides apear to confirm the compositional relatedness among these isozymes. The sequence of the loop region of mouse C subunit seems to be markedly different from all known A and B sequences, and the structural and functional implications are discussed.

Lactate dehydrogenase isozymes in the spermatozoa of the domestic fowl, Gallus domesticus and turkey, Meleagris gallopavo

1. Electrophoresis of extracts of turkey spermatozoa for lactate dehydrogenase activity revealed the usual five tissue LDHs (LDH-1 to LDH-5). 2. The presence of LDH-X (the spermatozoan-specific isozyme) was not obvious. 3. Only one band was present on electrophoresis of fowl spermatozoan extracts and it coincided with LDH-1 (heart type). 4. Kinetic investigations, the use of inhibitors and the heat-stability test confirmed that the fowl spermatozoan LDH was probably LDH-1 and not LDH-X.

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.

Mammalian oocytes: X chromosome activity

The glucose-6-phosphate dehydrogenase and lactate dehydrogenase contents of oocytes from XO and XX female mice have been measured. The activity of the former in the oocytes of XO mice is half of that in the oocytes of XX mice, whereas the lactate dehydrogenase activities in the two groups of ova are the same. These results indicate that glucose-6-phosphate dehydrogenase from a mouse oocyte is an X-linked enzyme, that its synthesis occurs in the oocyte and is dosage dependent, and that inactivation of the X chromosome does not occur in the mouse oocyte.