title: The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces changes in the heme spin state of microsomal cytochrome P-450.
abstract: In vitro studies on the nature of interaction of the neurotoxin MPTP with hepatic microsomal cytochrome P-450 were carried out. Spectral perturbation studies showed nitrogenous ligand type binding between MPTP and cytochrome P-450 with a peak at 423 nm and a broad trough at 400 nm. Scatchard analysis of MPTP-cytochrome P-450 binding suggested that MPTP binds to at least 2 species of cytochrome P-450--a high affinity binding species with an apparent spectral dissociation constant (Ks) of 372 microM and a low affinity species with Ks of 37.6 mM. EPR studies confirmed that MPTP is a type II substrate for the forms of cytochrome P-450 with which it interacts and causes a shift from the high spin state of cytochrome P-450 to the low spin state. MPTP is, thus, likely to be an effective inhibitor of cytochrome P-450.
authors.affiliation: Department of Physiology, National University of Singapore, Kent Ridge, Japan.
authors.forename: G S
authors.initials: GS
authors.lastname: Shahi
authors.forename: S M
authors.initials: SM
authors.lastname: Moochhala
authors.forename: N P
authors.initials: NP
authors.lastname: Das
authors.forename: J
authors.initials: J
authors.lastname: Sunamoto
authors.forename: K
authors.initials: K
authors.lastname: Tajima
mesh_terms: D000818:Animals; D001665:Binding Sites; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme; D066298:In Vitro Techniques; D007700:Kinetics; D020267:MPTP Poisoning; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D006418:Heme; D003577:Cytochrome P-450 Enzyme System