Epigenetic control of lactate dehydrogenase subunit assembly

Distribution and properties of lactate dehydrogenase isoenzymes in red and white muscle of freshwater fish

The distribution and kinetics of LDH isoenzymes in red and white muscles of 5 species of salmonids, 4 species of cyprinids and one coregonid species were studied. In all species the white muscles are characterized by the occurrence of only the most cathodic isoenzymes, or groups of isoenzymes. The red muscles contained either the full set of isoenzymes (cyprinids) or a selection in which the anodic forms dominated (salmonids, coregonid). The most striking difference between the two types of muscle was met inCoregonus sp. The temperature profiles of pyruvate affinity are similar in all species of fish studied. On the other hand, Km(pyr) values and degree of pyruvate inhibition are closely related and vary greatly with temperature, with the taxonomic position (and thus biology) of the species, and with electrophoresic mobility of the isoenzyme. Highest affinity and strongest inhibition occurred in the anodic (H4) isoenzymes of cyprinids at low temperature; lowest affinity and zero inhibition in the cathodic isoenzymes (Mα4 → Mβ4) of salmonids and coregonids at high temperature. In salmonids the more recently duplicated loci of the M-group of isoenzymes possess identical Km values at all temperatures, whereas the two older M and H loci differ greatly in this respect. Thus the more recent duplication of LDH loci in salmonids and coregonids may be seen as a mechanism by which the tetramers required for LDH activity can be constructed from more closely related subunits than are provided by the older M and H loci.Some problems in connection with the determination of the kinetic constants of the lactate oxidase reaction are discussed and it is suggested that an alkaline, pyruvate trapping system provides conditions which are more realistic than those of other assay systems. The Km(lactate) values found are in the biological range and, at 20°C, provide further circumstantial evidence that the red muscles of fish should be capable of oxidizing the lactate produced by the white muscles during strenuous exercise. At 4°C the Km(lactate) values are abnormally high in all muscle preparations and thus are not correlated with the Km(pyruvate) values which are lowest at this temperature.

Induction of lactate dehydrogenase by dibutyryl cAMP in primary cultures of central nervous tissue is an oligodendroglial marker

In vitro induction of lactate dehydrogenase (L-lactate:NAD+-oxidoreductase, EC 1.1.1.27, LDH) in response to catecholamines occurs in neural cell lines expressing glial properties. LDH is a tetrameric protein, consisting of two types of subunits: M-type or LDH-5 (predominant in skeletal muscle), and H-type or LDH-1 (predominant in heart muscle). These subunits are encoded by two nonallelic genes. Several studies have shown that LDH is induced by catecholamines via a cAMP-mediated process. We have previously shown that the mechanism of catecholamine induction for LDH in C6 glial cells involves an increase in the differential rates of synthesis of the two LDH subunits, suggesting that the regulation occurs at both genetic loci. Recently, a method has become available to prepare separate cultures of oligodendrocytes and astrocytes from newborn cerebral tissue. Both of these cultures markedly increase their intracellular cAMP concentration following a challenge by beta-adrenergic agonists. We have now investigated the regulation of LDH activity by dibutyryl cAMP (Bt2cAMP) in separate cultures of neurons, oligodendrocytes and astrocytes. The induction involving an increase in the rate of synthesis by Bt2cAMP is solely characteristic of oligodendrocytes. Moreover, both LDH genes contribute to this regulation.

Lactate dehydrogenase isozymes of mouse epidermis

Five isozymes of LDH are demonstrable in the epidermis of the ear pinnae, hind feet, trunk dorsa, and tails of adult C57BL, C57HR, and C3HB mice by polyacrylamide gel electrophoresis. LDH-5 activity predominates in electropherograms. The ratio of LDH-1 to LDH-K is greater in the epidermis of ear pinna and trunk dorsum than in that of tail and hind foot. The region-specific patterns of epidermal LDH isozymes are not correlated with melanin pigmentation or "hairiness' of the skin.

Ontogeny of lactate dehydrogenase isozymes in chicken-quail hybrid embryos

The ontogeny of lactate dehydrogenase (LDH) isozymes was examined in avian hybrids and compared with the isozyme patterns of the parental species. Hybrids were obtained by crossing female Japanese quali (Coturnix coturnix japonica) with male domestic chickens (Gallus gallus domesticus). By use of starch gel electrophoresis and an enzyme-specific stain, traces of embryonic paternally derived LDH were detected in unincubated hybrid eggs. It was concluded that the embryonic genes coding for the B subunits of LDH are activated during the hours between fertilization and oviposition. In early blastoderms, a great excess of maternally stored LDH is present. In the hybrid, the predominantly maternal pattern of isozymes shifts during embryogenesis to a predominantly paternal pattern. This was considered evidence for differential allelic regulation of LDH inactivation. A progressive trend toward the establishment of the adult distribution of isozymes in various tissues was also observed in the hybrid and quail, and found to be similar to chicken LDH isozyme ontogeny.