Occurrence of β-alanine-specific opine dehydrogenase in the muscle of the limpet Cellana grata Gould (Archaeogastropoda)

The muscular tissues of the limpet Cellana grata exhibited β-alanopine dehydrogenase (β-AlDH) activity in addition to tauropine dehydrogenase (TaDH) activity and weak lactate dehydrogenase activity. Opine dehydrogenases (OpDHs) were purified, and two different types of OpDH, i.e. TaDHs and OpDHs showing β-AlDH activity, were isolated. From the specificity for amino acid and opine, OpDHs showing β-AlDH activity were concluded to be a true β-AlDH showing strict substrate specificity for β-alanine. Although the catalytic properties of β-AlDH and TaDH were essentially similar, they were distinct from each other with respect to the amino acid substrate specificity and the K(m) values. Apparent K(m) values (mM) for the preferred amino acid substrate, pyruvate, NADH, the preferred opine substrate, and NAD⁺ were: 14.3 (β-alanine), 0.19, 0.032, 35.2 (β-alanopine), and 0.78 for β-AlDH; and 33.3 (taurine), 0.53, 0.076, 48.6 (tauropine), and 0.58 for TaDH, respectively. Great similarities were found between β-AlDH and TaDH with respect to molecular properties: molecular masses (both enzymes were monomeric proteins of approximately 40 000 Da), amino acid compositions, and N-terminal amino acid sequences (30 amino acid residues were identical). Partial similarities were also recognized between their lysyl endopeptidase maps. These results clearly show that β-alanine-specific OpDH, a true β-AlDH, is present in the limpet muscle. Copyright (C) 1999 Elsevier Science Inc.