ISOLATION AND CHARACTERIZATION OF CDNA-ENCODING CHICKEN EGG-YOLK AMINOPEPTIDASE EY

Aminopeptidase Ey (EC 3.4.11.20) from chicken (Gallus gallus domesticu s) egg yolk is a homodimeric exopeptidase with a broad specificity for N-terminal amino acid residues at P-1 position of the substrate. Amin opeptidase Ey is a 300-k metalloexopeptidase, containing 1.0 g atom of zinc per mole of a subunit with a relative molecular mass of 150 k, A full-length cDNA was cloned from chicken (female) liver cDNA library. Analysis of the 3196-base pairs (bp) nucleotide sequence of the cDNA revealed a single open reading frame coding for 967 amino acid residue s. The coding region of aminopeptidase Ey gene, apdE, occupies 2901 bp of the cDNA. The predicted amino acid sequence of the enzyme is 66, 6 5, 64 and 63% identical with those of aminopeptidases N (EC 3.4.11.2) from human, pig, rabbit and rat, respectively. Aminopeptidase Ey conta ins the metallo-binding sequence motif, His-Glu-Xaa-Xaa-His, found in zinc metallopeptidases. Zinc binding sites, His-386, His-390 and Glu-4 09, and catalytic site, Glu-387, were conserved in the homologous amin opeptidases N. (C) 1998 Elsevier Science Inc. All rights reserved.