Alanopine and strombine are novel imino acids produced by a dehydrogenase found in the adductor muscle of the oyster, Crassostrea gigas

Previous work on anaerobic metabolism in the heart of the oyster indicated the formation of an unidentified compound as a product of amino acid utilization during anoxia. A dehydrogenase, present in the adductor muscle and heart of the oyster, was found to utilize reduced nicotinamide adenine dinucleotide, pyruvic acid, and alanine or glycine as substrates. The stoichiometry of the reaction suggested the enzyme was similar to octopine dehydrogenase (EC 1.5.1.11), which is known to form the imino acid N 2 -(1-carboxyethyl)-arginine (octopine). Incubation of the enzyme with reduced nicotinamide adenine dinucleotide, alanine, and pyruvic acid gave a product identified as 2,2′-iminodipropionic acid (alanopine) on the basis of both physical and chemical data. Either synthetic alanopine or strombine reacted with the enzyme and nicotinamide adenine dinucleotide, which indicated the free reversibility of the reaction. This enzyme probably functions in the maintenance of a redox balance during anaerobiosis in the adductor muscle and heart of the oyster.