Partial purification and characterization of the oxytocin-inactivating enzymes from chicken liver.
1. Two enzymes acting on the linear portion of oxytocin: carboxamidopeptidase (releasing Gly . NH2) and prolyl peptidase (releasing Leu-Gly . NH2) were identified in the cytoplasmic fraction of chicken liver. 2. Carboxamidopeptidase was purified 134-fold with a 23% yield, and prolyl peptiase 71-fold with a 20% yield. The specific activity of the final preparations was 181 and 96 microU/mg protein, respectively. 3. The optimum pH for carboxamidopeptidase was 6.0--6.5 and for prolyl peptidase, 7.5. Carboxamidopeptidase activity was inhibited by Mn2+, Zn2+, Ca2+, Co2+, and stimulated by EDTA; the activity of prolyl peptidase was inhibited by Zn2+ and Mn2+. The Km value of both enzymes for oxytocin was 1.5--2.4 microM.
D000818:Animals; D002645:Chickens; D002852:Chromatography, Ion Exchange / Q000379:methods; D003593:Cytoplasm / Q000201:enzymology*; D010450:Endopeptidases / Q000302:isolation & purification*; D005260:Female; D006727:Hormone Antagonists; D008099:Liver / Q000201:enzymology*; D010121:Oxytocin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors*; D000085822:Prolyl Oligopeptidases; D051381:Rats; D012697:Serine Endopeptidases
D006727:Hormone Antagonists; C010851:oxytocin, 1,6-alpha-Asu-; C024672:oxytocin, deamino-1-carba-; D010121:Oxytocin; D010450:Endopeptidases; D012697:Serine Endopeptidases; C023904:carboxamidopeptidase; D000085822:Prolyl Oligopeptidases