Activities of adenylate-degrading enzymes in muscles from vertebrates and invertebrates.

Activities of adenylate-degrading enzymes in muscles of vertebrates and invertebrates were determined. Mammalian and fish muscles showed a markedly higher activity of AMP deaminase with a lower level of adenosine deaminase and 5'-nucleotidase. Cephalopods showed an active adenosine deaminase and a 5'-nucleotidase which preferred AMP as the substrate. Negligible deamination of AMP and adenosine and little phosphohydrolase activity toward AMP and IMP were observed in the shellfish muscles. Adenine nucleotides can be degraded to form IMP via the AMP deaminase reaction in vertebrate muscles, while dephosphorylation of AMP to adenosine, which is then converted to inosine, appears to proceed in cephalopods. Adenylates can be hardly degraded in shellfish muscles.