title: Phosphoryl group transfer by a fraction of the soluble proteins of catecholamine storage vesicles.
abstract: The terminal phosphate group of ATP was transferred to ADP by an enzyme present in the soluble core proteins of adrenal medulla catecholamine storage vesicles. It was purified 10-30-fold by DEAE Sephadex chromatography (Fraction I). The enzyme required divalent metal ions for activation; Mn2+ was almost as effective as Mg2+, but Ca2+ was only a weak activator. Activation by Mg2+ took place over a very narrow concentration range (0.5-3 mM). The specificity of the enzyme activity to nucleoside triphosphates was broad, to the nucleoside diphosphates narrow, favouring adenosine diphosphate. In dependence on the pH the activity increased from pH 4 to pH 7 and remained constantly high between pH 7 and 9. The Arrhenius plot was linear between 5 and 70 degrees C, with an activation energy of 11.1 kcal/mol. The phosphoryl group transfer reaction depended on the function of thiol groups; p-hydroxymercuribenzoate inhibited 50% of the enzyme activity; dithioerythritol reactivated it completely. Gel electrophoresis revealed that in Fraction I, a protein of molecular weight about 45,000, was enriched compared with the total proteins. The enzyme-enriched Fraction I differed significantly in its relative amino acid composition from that of the total soluble proteins; in general, the acidic amino acids were reduced and the more basic acids enhanced.
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000263:Adenylate Kinase / Q000378:metabolism; D000313:Adrenal Medulla / Q000201:enzymology*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D004229:Dithiothreitol / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D006902:Hydroxymercuribenzoates / Q000494:pharmacology; D008247:Lysosomes / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D006902:Hydroxymercuribenzoates; C030601:4-hydroxymercuribenzoate; D008345:Manganese; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000263:Adenylate Kinase; D008274:Magnesium; D005033:Ethylmaleimide; D002118:Calcium; D004229:Dithiothreitol