The distribution of isoenzymes of lactate dehydrogenase (LDH) and aspartate aminotransferase (Apa'H') in the tissues of 189 herrin (Qupea hawngus ktareagus L.) were examined. Starch-gel electrophoresis of the L~H isoenzymes of the herring revealed the presence of two hybrid forms representing mutant alleles at the B locus. These mutants gave rise to two genotypes, BBQnd BBrP, whose LDH staining patterns revealed a binomial distribution of the tetramer combinations formed from a free and random association of the A, B, and B', and the A, B, and B" monomers respectively. A hybrid form of soluble AAT was found. Its electrophoretic pattern showed a 1:2:1 binomial distribution of bands. It is postulated that these bands represent ,\AT dimers formed from normal S and mutant SP monomers of a heterozygous SS' genotype. The normal homozygous SS genotype showed only one band of activity. The normal levels of LDH and IUT activity in plasma and in heart and skeletal nauscles were determined. During frozen storage LDH-5 activity gradually disappeared, while LDH-1 activity changed least; LBH-1 was also most stable at higher temperatures. Frozen storage rapidly destroyed AAT activity. AppeIla and Marker$ (1) demonstrated that the enzyme lactate delaydrsgenase (LDH)l is a tetramer, which was subsequentIy shown to consist of two different kinds sf monomers designated "A9' and 46Bv' by hIarkert (2). The 66A0 and 66Bpp monomers are urnder control of separate genetic loci and the association of these two monomers into tetramers gives rise to the five isoenzymes of LDH in mammalian tissues. Sub-banding of the five isoenzymes is frequently observed, and in a recent review Markert (3) suggested three explanations: (i) the existence of additional monomers under the control of further genetic loci (such as the "C" subunit found in sperm by Blanco and Zinkham (4)) ; (ii) permutations sf the monomers within the five major bands, (e.g. a tetrmer with a monomer sequence ABAB might differ in mobility from a tetramer of the saille subunit composition but with a different monomer sequence ABBA) ; and (iii) the existence of mutant alleles at any 0% the existing loci. The LDH patterins of fish differ considerably from the mammalian pattern sf five bands. Ibfarkert and Faulhaber (5) studied 30 species and found fish with I, 2, 3, or 5 LDH isoenzymes. They suggest that factors such as subunit charge and molecular configuration afFect the combination of fish LDW monomers more than the mammalian monomers. Thus some subunit associations are preferred and most fish fail to show all five major LDH isoenzyme bands. IL-Lactatei NAD oxidorductase (EC 1.1.1.27).
