title: Peptide C-terminal alpha-amidating enzyme purified to homogeneity from Xenopus laevis skin.
abstract: The C-terminal alpha-amide formation of the peptides is one of the most important events of prohormone processing. In this study, we have developed a simple and sensitive assay for monitoring alpha-amidating activity by using radioiodinated Ac-Tyr-Phe-Gly as a substrate. By utilizing this assay, an alpha-amidating enzyme was first purified to homogeneity from Xenopus laevis skin. The purified enzyme has a single polypeptide chain with an apparent molecular weight of 39,000 and its N-terminal sequence was determined as Ser-Leu-Ser-. The enzyme converts several synthetic peptides with C-terminal glycine to the corresponding des-glycine peptide alpha-amides. The enzyme activity, with an optimal pH 6-7, was dependent on the copper ion and ascorbate. In the presence of 0.25 mM ascorbate, the enzyme exhibited a Km of 0.35 microM and a Vmax of 1.9 nmol/microgram/h for Ac-Tyr-Phe-Gly.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002845:Chromatography; D006899:Mixed Function Oxygenases; D008970:Molecular Weight; D009097:Multienzyme Complexes; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000302:isolation & purification* / Q000378:metabolism; D012867:Skin / Q000201:enzymology; D013379:Substrate Specificity; D014982:Xenopus laevis
chemical_list: D009097:Multienzyme Complexes; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase; D000587:Oxidoreductases Acting on CH-NH Group Donors