Genetic basis of opine dehydrogenase activities in the Pacific oyster, Crassostrea gigas

Abstract

Two polymorphic gene loci coding for enzyme proteins responsible for multiple opine dehydrogenase activities are expressed in the adductor muscle of the Pacific oyster, Crassostrea gigas. One locus, Strdh( Alpdh-1), codes for an isozyme that demonstrates highest catalytic activity with glycine, but is also capable of using α- l-alanine, l-serine and β-alanine as substrates. The second locus, Alpdh- 2, codes for an isozyme specific to α- l-alanine. Electrophoretic gels stained using α- l-alanine as substrate reveal presence of both isozymes in adductor muscle tissues. The STRDH(ALPDH-1) isozyme alone is detected in adductor muscle, with glycine as substrate, whereas only ALPDH-2 is detected in hepatopancreas, mantle and gill tissues with α- l-alanine. Only two enzyme proteins are responsible for multiple opine dehydrogenase activities in the adductor muscle of the oyster. The value of gene-enzyme specific allozyme patterns for identification of, and discrimination between, enzyme proteins possessing broad substrate specificity is briefly discussed.