title: Properties of membrane bound ferrochelatase purified from baboon liver mitochondria.
abstract: 1. Baboon ferrochelatase was purified to apparent homogeneity. 2. The pH optimum was 7.85 and the pI 5.3. 3. The estimated molecular weight was 205 K made up by two 50 + 60 K heterodimers. 4. The Km values for proto- and mesoporphyrin were 18.5 and 10.8 microM with iron as co-substrate. With cobalt as co-substrate the Km values were 34.5 and 10.4 microM, respectively. The mean Km value for iron was 2.2 microM while cobalt acted as a complete inhibitor. 5. Lead played a dual role that of both pseudo substrate and inhibitor. As shown by inhibitor kinetics, Pb acted as a two-step two-site parabolic competitive inhibitor. The mean Ki value at low Pb levels was 0.65 mM and at high levels 0.17 mM. 6. Substrate inhibition occurred above 36 microM for proto- and 44 microM for mesoporphyrin with iron as co-substrate. For iron, with mesoporphyrin as co-substrate it occurred above 29 microM.
authors.affiliation: Department of Surgery, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: S J
authors.initials: SJ
authors.lastname: Posnett
authors.forename: M M
authors.initials: MM
authors.lastname: Oosthuizen
authors.forename: A C
authors.initials: AC
authors.lastname: Cantrell
authors.forename: J A
authors.initials: JA
authors.lastname: Myburgh
mesh_terms: D000818:Animals; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005294:Ferrochelatase / Q000032:analysis* / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007854:Lead / Q000494:pharmacology; D008190:Lyases / Q000032:analysis*; D008565:Membrane Proteins / Q000032:analysis* / Q000302:isolation & purification; D008670:Metals / Q000378:metabolism; D008930:Mitochondria, Liver / Q000201:enzymology*; D008970:Molecular Weight; D010100:Oxygen / Q000494:pharmacology; D010215:Papio; D012995:Solubility; D013379:Substrate Specificity
chemical_list: D008565:Membrane Proteins; D008670:Metals; D007854:Lead; D008190:Lyases; D005294:Ferrochelatase; D010100:Oxygen