Enkephalin hydrolysis by human serum biotinidase.
Purified human serum biotinidase exhibited amino-exo-peptidase activity. Enkephalins and dynorphin A (less than 10-mer) seemed to be the most appropriate substrates among various physiological peptides in terms of the kcat/Km values. Similar kcat/Km values were obtained for both biocytin (biotinyllysine) and these opioid-neuropeptides. Neuro-oligo-peptides ranging from 2-mer to 18-mer were hydrolyzed. The presence of amino group at the carboxyl terminal position increased the kcat/Km value by decreasing the Km value. The results of inhibition studies using various kinds of antibiotic inhibitors, metals, and chelating agents indicated that enkephalin hydrolysis was mediated by the peptide-hydrolyzing center probably containing Zn ions. This aminopeptidase activity was uniquely inhibited by a vitamin of biocytin. The reason for the high content of biotinidase activity in serum may be related to the binary function of this enzyme; i.e., biocytin hydrolyzing amidase and enkephalin hydrolyzing aminopeptidase functions.
National Children's Medical Research Center, Tokyo, Japan.
J
J
Oizumi
K
K
Hayakawa
D000581:Amidohydrolases / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism*; D000595:Amino Acid Sequence; D043523:Biotinidase; D004399:Dynorphins / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004723:Endorphins / Q000378:metabolism; D004745:Enkephalins / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008239:Lysine / Q000031:analogs & derivatives / Q000494:pharmacology; D008969:Molecular Sequence Data; D013379:Substrate Specificity; D014815:Vitamins / Q000494:pharmacology
D004723:Endorphins; D004745:Enkephalins; D014815:Vitamins; D004399:Dynorphins; D000581:Amidohydrolases; D043523:Biotinidase; C013411:biocytin; D008239:Lysine