Distribution of AMP Deaminase and Adenosine Deaminase in Muscle of Mammals, Fish, Molluscs and Crustaceans

Abstract

Accumulation of IMP, one of the important taste substances, is accompanied by the decrease in adenine nucleotides in muscles at the stage of rigor mortis. Muscle ATP is dephosphorylated to ADP and further to AMP, which can be converted to IMP by the action of AMP deaminase. In this paper the distribution of AMP deaminase, which acts as a regulatory enzyme in the adenylate degradation to form IMP, was examined and the levels of AMP deaminase activity was compared to those of adenosine deaminase activity. Possible pathways of adenylate degradation are discussed in various vertebrate and invertebrate muscles.
A remarkably higher activity of AMP deaminase and a marked lower activity of adenosine deaminase were observed in muscles of a variety of vertebrates. In contrast to vertebrates, cephalopods in invertebrates showed a marked higher adenosine deaminase activity with lower activity of AMP deaminase. Negligible deaminating activity toward AMP and adenosine was observed in the muscles of some invertebrates including crustaceans, gastropods and bivalves.
A close correlation of the IMP content with flavor has been demonstrated in vertebrate meats, and the higher enzymatic activity of AMP deamination will contribute to the IMP content of vertebrates. However, lower activity of AMP deaminase will not contribute to the IMP content of invertebrate muscles. Little or no degradation of adenine nucleotides and nucleosides in crustaceans, gastropods and bivalves was in accord with the stable pool of adenylates during storage of these muscles. Higher activity of adenosine deaminase with a lower AMP deaminase activity suggests that adenine nucleotides degrade via the dephosphorylation followed by deamination.