Mechanism of porphobilinogen synthase. Requirement of Zn2+ for enzyme activity.

摘要: The role of metal ions in the mechanism action bovine liver porphobilinogen synthase was investigated. Studies with chelating agents were consistent a requirement for enzyme activity, and use 8-hydroxyquinoline-5-sulfonic acid suggested that Zn2+ present enzyme. low activity detected metal-free apoporphobilinogen attributed to adventitious ions. Addition apoenzyme completely restored if essential sulfhydryl groups on first reduced reagents. It does not follow necessarily from this observation forms bond group However, we also observed did bind unless cysteinyl residues reduced. We have concluded octameric contains 4 g atoms Zn2+/mol our measurements binding studies. Alkylation resulted marked reduction These observations are suggestion interaction occurs at active site. appears participate substrate nor maintenance quaternary structure Possible mechanistic roles discussed. should be noted Cd2+ only other element found which apoenzyme.