Two enzymes concerned in peptide hormone α-amidation are synthesized from a single mRNA

By expressing truncated rat pituitary 'peptidylglycine α-amidating enzyme' cDNAs in COS-7 cells, we found that the two reactions concerned in peptide carboxyl-terminal amidation, namely the peptidylglycine α-hydroxylation reaction and the peptidyl-hydroxyglycine amidation reaction, were catalyzed by 37-and 53-K proteins, which were derived from the 5′- and 3′-coding sequences, respectively. The full-length cDNA directed the expression of both the 37- and 53-K enzymes, and in the combined presence of the two enzymes the full conversion of a glycine-extended peptide into the amidated product was achieved. These results indicated that two enzymes concerned in peptide hormone α-amidation are generated from a common precursor protein encoded by a single mRNA.