Substrate-induced spin-state transition in cytochrome P450LM2: a temperature-jump relaxation study.
The kinetics of the benzphetamine-P450LM2 binding reaction were studied by the T-jump relaxation technique, using the substrate-induced type I spectral change (which reflects transformation of the heme from the low- to the high-spin state) as the criterion for binding. The reciprocal relaxation time (kobs) exhibited a linear dependence on [E]eq+[S]eq. The kinetically determined dissociation equilibrium constant (68 +/- 10 microM) and that determined by direct titration of the spectral change (61 +/- 4 microM) were very similar. These results indicate that the substrate-induced spin-state transition follows a simple biomolecular binding mechanism; that is, the substrate-induced low- to high-spin transition reflects substrate binding.
Harrison Department for Surgical Research, University of Pennsylvania, Philadelphia 19104.
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Narasimhulu
D000818:Animals; D001589:Benzphetamine / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D011817:Rabbits; D013053:Spectrophotometry; D013696:Temperature
D001589:Benzphetamine; D003577:Cytochrome P-450 Enzyme System