title: Inactivation of C3a by a monocarboxypeptidase present in culture supernatants of stimulated guinea pig peritoneal macrophages.
abstract: Hog C3a, as well as its derivative C3a-desArg were not found to act cytotoxically on starch gel-induced guinea pig peritoneal macrophages. Likewise, neither peptide significantly modified the secretion of N-acetyl-beta-D-glucosaminidase from these cells. However, C3a rapidly lost its spasmogenic activity during incubation in serum-free macrophage cultures and less rapidly in cellfree supernatants collected from cultured macrophages. The following results indicate that C3a is converted into its spasmogenically inactive derivative C3a-desArg by a macrophage-derived monocarboxypeptidase. The inactivated C3a product does not differ from native C3a in sodium dodecyl sulfate-polyacrylamide gel electrophoresis; it elutes from CM cellulose in the same position as purified C3a-desArg; and it is devoid of the carboxyl-terminal arginyl residue of C3a, but still contains the carboxyl-terminal sequence of C3a-desArg as determined by analysis after treatment with carboxypeptidases B or Y. Furthermore, inactivation of C3a in supernatants of macrophage cultures is completely blocked by the specific carboxypeptidase inhibitors guanidinopropylsuccinic acid and 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid in final concentrations of 10 mM and 2.1 mM, respectively. The monocarboxypeptidase is apparently supplied by biosynthesis of new material but is not stored as a preformed enzyme because cycloheximide markedly inhibits its expression.
mesh_terms: D000118:Acetylglucosaminidase / Q000378:metabolism; D000818:Animals; D002268:Carboxypeptidases / Q000494:pharmacology*; D002474:Cell-Free System; D002478:Cells, Cultured; D002852:Chromatography, Ion Exchange; D003176:Complement C3 / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology / Q000502:physiology; D015926:Complement C3a; D003169:Complement Inactivator Proteins / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008262:Macrophage Activation; D008264:Macrophages / Q000201:enzymology* / Q000276:immunology; D009119:Muscle Contraction / Q000187:drug effects; D013552:Swine
chemical_list: D003176:Complement C3; D003169:Complement Inactivator Proteins; C044541:complement C3a, des-Arg-(77)-; D015926:Complement C3a; D007770:L-Lactate Dehydrogenase; D000118:Acetylglucosaminidase; D002268:Carboxypeptidases