THE AMINO-ACID-SEQUENCES OF 2 ACYLPHOSPHATASE ISOFORMS FROM FISH MUSCLE (LAMNA-NASUS)

Two acylphosphatase isoenzymes have been purified from Lamna nasus mus cle, and their complete amino acid sequences have been determined, The former (El) consists of 99 amino acid residues, while the latter (E2) consists of 102 residues. Both are acetylated at their N termini. El has the FFRK active site motif characteristic of all common-type acylp hosphatase isoenzymes, whereas E2 contains the CFRM active site motif characteristic of all muscle-type acylphosphatase isoenzymes. They hav e quite similar kinetic properties. The comparison of sequences of fis h El and E2 isoenzymes with other known mammalian and bird acylphospha tases reveals that the E2 isoenzyme has an N terminus tail, four resid ues long, similar to those previously found in all known bird species muscle-type isoenzymes. Among organ-common-type acylphosphatases about 50% of residues are completely conserved, whereas about 60% of muscle -type acylphosphatase residues are completely conserved, indicating th at the latter type of isoenzyme has a slower evolutionary rate than th e former. The sequences of El and E2 acylphosphatases from L. nasus re present the first primary structures of this kind of enzyme determined among fish species. (C) 1998 Elsevier Science B.V. All rights reserve d.