Possible Significance of the Isoenzymes of Lactic Dehydrogenase in the Retina of the Rat

VARIOUS physico-chemical techniques have been recently used to reveal the heterogeneity of the enzyme lactic acid dehydrogenase. On the basis of investigations of this enzyme in tissues of the chicken, Cahn et al. 1 have suggested that, although five fractions are identifiable, three of these represent hybrids of the two major and discrete fractions, the M and H isoenzymes. This designation is derived from the observation that the former predominates in skeletal muscle, and thelatter in heart tissue. These authors consider, in fact, that the five fractions arise from a permutation of four sub-units, each type containing a different proportion of the M and H enzymes, and being designated as M , M 3 H 1, M 2 H 2, M 1 H 3 and H .