Identification in pituitary tissue of a peptide alpha-amidation activity that acts on glycine-extended peptides and requires molecular oxygen, copper, and ascorbic acid.
AUTOR(ES)
Eipper, B A
RESUMO
An enzymatic activity capable of producing an alpha-amidated peptide product from its glycine-extended precursor has been identified in secretory granules of rat anterior, intermediate, and neural pituitary and bovine intermediate pituitary. High levels of endogenous inhibitors of this alpha-amidation activity have also been found in tissue homogenates. The alpha-amidation activity is totally inhibited by addition of divalent metal ion chelators such as diethyldithiocarbamate, o-phenanthroline, and EDTA; alpha-amidation activity is restored to above control levels upon addition of copper. The alpha-amidation reaction requires the presence of molecular oxygen. Of the various cofactors tested, ascorbic acid was the most potent stimulator of alpha-amidation. The alpha-amidation activity has a neutral pH optimum and is primarily soluble following several cycles of freezing and thawing. Kinetic studies with the bovine intermediate pituitary granule-associated activity demonstrated a linear Lineweaver-Burk plot when D-Tyr-Val-Gly was the varied substrate; the apparent Km and Vmax varied with the concentration of ascorbic acid. The substrate specificity of the alpha-amidation activity appears to be quite broad; the conversion of D-Tyr-Val-Gly into D-Tyr-Val-NH2 is inhibited by the addition of a variety of glycine-extended peptides.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=384206Documentos Relacionados
- Overexpression of glycine-extended gastrin in transgenic mice results in increased colonic proliferation
- Killing of Bacillus Spores by Aqueous Dissolved Oxygen, Ascorbic Acid, and Copper Ions
- Exocrine secretion granules contain peptide amidation activity.
- Regulation of collagen synthesis by ascorbic acid.
- Absorption of Copper, Zinc, and Manganese by Sugarcane Leaf Tissue 1