Catalytic properties of the sperm‐specific lactate dehydrogenase (LDH X or C₄) from different species

Abstract

A comparative study of catalytic properties of the sperm-specific lactate dehydrogenase (EC 1.1.1.27) isozyme X or C4 from a variety of animals (boar, bull, goat, Guinea pig, man, mouse, pigeon, rabbit, and rat) is presented. Optimum concentration and Km values for pyruvate, inhibition by substrate, and activity against analog substrates (alpha-ketoacids with linear and branched chains from 4 to 6 carbon atoms) for isozyme X of different species showed significant differences. The observed properties are correlated with available evidence on the metabolic role of the enzyme.

Oxamic acid analogues as LDH-C4-specific competitive inhibitors

“…7,8,10,21 All LDH isozymes catalyse the reaction from pyruvate to lactate and from lactate to pyruvate. However, the LDH-C4 shows activity towards α-keto and α-hydroxy acid, of longer carbon chain than those of pyruvate and lactate (Figure 1).…”

“…[5][6][7] LDH-C4 is more sensitive to pyruvate inhibition and less sensitive to lactate inhibition and, consequently, is believed to perform as a lactate oxidase. It has been proposed that the physiological function of LDH-C4 is to generate the reducing equivalents necessary for sperm motility from the high concentrations of lactate found in the female reproductive tract.…”

Trypanosoma cruzi: inhibition of alpha-hydroxyacid dehydrogenase isozyme II by N-allyl and N-propyl oxamates and their effects on intact epimastigotes

“…This T. cruzi enzyme is a NAD-linked oxidoreductase whose catalytic properties resemble those of mouse and rat (Coronel et al 1983) LDH-C4. The enzyme designated as α-hydroxyacid dehydrogenase (HADH), exhibits two molecular forms (I and II), which have been purified and characterized from the point of view of substrate specificity and kinetic constants (Gerez de Burgos et al 1978).…”

Energy Management of Mature Mammalian Spermatozoa

“…However, sperm utilization of citrate and lactate has several specific features. Thus, a sperm-specific lactate dehydrogenase (LDH) isozyme has been described in several species [12,27,37,40,41]. This specific isozyme, named LDH-X is the most important LDH form in sperm in which it has been described, such as boar [27], whereas its activity presents several differentiate features.…”