Enkephalin-degrading dipeptidyl carboxypeptidase in guinea pig serum: its properties and action on bioactive peptides.
A dipeptidyl carboxypeptidase, which cleaved the Gly3-Phe4 bond of enkephalins, was purified from guinea pig serum 420-fold. The optimum pH of the enzyme was in the neutral range (pH 7.25), and the molecular weight was estimated to be approx. 280,000. The enzyme hydrolyzed Met- and Leu-enkephalin with Km values of 0.30 and 0.50 mM, respectively. The enzyme was inhibited by metal chelators and p-chloro-mercuribenzoate. Captopril showed high inhibitory potency, while phosphoramidon and Phe-Ala showed no effect on the enzyme activity. Therefore, the obtained enzyme can be classified as an angiotensin-converting enzyme (EC 3.4.15.1). Among the bioactive peptides examined, bradykinin and angiotensin I were hydrolyzed by the enzyme. Angiotensin III showed a stronger inhibitory effect than that of angiotensin II. Substance P, gastrin I, and secretin were also inhibitory toward the enzyme activity. On high-performance liquid chromatography analysis, Met-enkephalin-Arg6-Phe7 and Leu-enkephalin-Arg6 were cleaved sequentially at the second peptide bond of the C terminus. Thus, the dipeptidyl carboxypeptidase in guinea pig serum may play a role not only in the angiotensin-bradykinin system but also in the metabolism of circulating enkephalins and other bioactive peptides.
Kase
R
R
Hazato
T
T
Shimamura
M
M
Kiuchi
Y
Y
Katayama
T
T
D000818:Animals; D001345:Autoradiography; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D010450:Endopeptidases / Q000097:blood* / Q000302:isolation & purification; D004745:Enkephalins / Q000097:blood*; D006168:Guinea Pigs; D006868:Hydrolysis; D008970:Molecular Weight; D007703:Peptidyl-Dipeptidase A / Q000097:blood; D011480:Protease Inhibitors
D004745:Enkephalins; D011480:Protease Inhibitors; D010450:Endopeptidases; C020071:dipeptidyl carboxypeptidase; D007703:Peptidyl-Dipeptidase A