Molecular cloning, sequence analysis and expression distribution of an aminopeptidase in Aplysia californica

We are investigating the role of membrane-bound peptidases in the inactivat ion of neuropeptides in Aplysia californica. Recently, we reported the bioc hemical characterization of a membrane-bound neuropeptide-degrading enzyme which has enzymatic characteristics similar to those of the mammalian amino peptidase N (Bawab W, Querido E, Crine P, DesGroseillers L. Identification and characterization of aminopeptidases from Aplysia californica, Biochem J 1992;286:967-975). We now report the cloning and sequencing of a cDNA enco ding an aminopeptidase enzyme (apAP) and the localization of the apAP trans cript in Aplysia. The apAP cDNA encodes a putative protein of 1007 amino ac ids, which shows around 34% sequence identity to mammalian aminopeptidases A and N sequences. The deduced amino acid sequence suggests that apAP is a type II membrane-bound protein, with a long extracellular domain in which t he consensus sequence of zinc-binding metallopeptidases (His-Glu-Xxx-Xxx-Hi s) is found. RT-PCR and Northern blot experiments showed that the apAP gene is expressed as a single 6.8-kb transcript in the central nervous system, gill, heart, kidney and ovotestis. (C) 1999 Elsevier Science Inc. All right s reserved.