The hybrid lactic dehydrogenases H2M2 from chicken liver and HM3 from chicken leg muscle have been isolated and crystallized. The pure H4 form of the enzyme has been isolated and crystallized from chicken liver and compared to the H4 obtained from heart. Fingerprint patterns of tryptic digests of the hybrids have been compared to patterns obtained from a 1:1 mixture of the H4 and M4 and have shown the hybrids to be a combination of the pure forms. Amino acid analyses, particularly of histidine, place the hybrids at points intermediate between the pure types. The H4 from chicken liver did not vary significantly in amino acid content or molecular weight from the H4 obtained from chicken heart. Molecular weights of the hybrids were in the same range as those of the pure types. Heat and time stability studies of the chicken hybrids and of beef hybrids isolated from starch grain have established the intermediate nature of the hybrids. Immunological properties, analog ratios, and oxalate inhibition also demonstrate that the hybrids are combinations of the H4 and M4 forms of the enzyme.
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