Purification and cDNA cloning of <i>Xenopus laevis</i> skin peptidylhydroxyglycine N‐C lyase, catalyzing the second reaction of C‐terminal α‐amidation

Abstract

The α‐amidation of glycine‐extended peptides is a two‐step reaction catalyzed by peptidylglycine α‐hydroxylating monooxygenase (PHM) and peptidylhydroxyglycine N‐C lyase (PHL). PHL was purified to homogeneity from Xenopus laevis skin and its partial amino acid sequene (including the N‐terminal 35 residues) was determined. A cDNA, termed AE‐III, encoding X leavis PHL, was cloned and its complete nucleotide sequence was determined. It was found that the cDNA codes for a 935‐residue precursor protein (AE‐III protein), containing the PHM and PHL sequences at its N terminus and C terminus, respectively. The PHM sequence in AE‐III protein is completely identical to that deduced from the nucleotide sequence of X. laevis AE‐I cDNA, which encodes only PHM, except that the AE‐I protein has an extra 10 residues at its C terminus. It is suggested that AE‐I and AE‐III mRNA are encoded by the same gene and produced by alternative splicing.