Hypothalamic peptidyl-glycine alpha-amidating monooxygenase: preliminary characterization.

Emeson RB
J Neurosci. 1984 4 (10): 2604-13

PMID: 6491725

An enzymatic activity capable of converting mono-[125I]-D-Tyr-Val-Gly into mono-[125I]-D-Tyr-Val-NH2 was identified in a crude mitochondrial/synaptosomal preparation from rat hypothalamus. Further subcellular fractionation studies localized a majority of this enzymatic activity to fractions enriched in synaptic vesicles. The alpha-amidation activity demonstrated optimal activity at pH 7.5 to 8, was stimulated by the presence of copper ions and reduced ascorbate and required the presence of molecular oxygen. Endogenous alpha-amidation activity was inhibited by the addition of ascorbate oxidase. Kinetic analyses demonstrated Michaelis-Menten type kinetics for D-Tyr-Val-Gly as the varied substrate with the values of Km and Vmax increasing as the ascorbate concentration in the reaction increased. A variety of peptides possessing carboxyl-terminal glycine residues were potent inhibitors of the reaction, while peptides lacking a carboxyl-terminal glycine residue were not, suggesting that many glycine-extended peptides may serve as substrates in the alpha-amidation reaction. The characteristics of hypothalamic alpha-amidation activity are similar to those previously reported for the alpha-amidation activity in rat pituitary and mouse corticotropic tumor cells suggesting the presence of closely related enzymes in these tissues.

MeSH Terms (15)

Animals Chemical Phenomena Chemistry Copper Hypothalamus Kinetics Male Mixed Function Oxygenases Multienzyme Complexes Oxidoreductases Acting on CH-NH Group Donors Oxygen Rats Rats, Inbred Strains Synaptic Vesicles Tissue Extracts

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