Mechanism of cytochrome P450 reductase from the house fly: evidence for an FMN semiquinone as electron donor
Open Access
- 17 June 1999
- journal article
- Published by Wiley in FEBS Letters
- Vol. 453 (1-2) , 201-204
- https://doi.org/10.1016/s0014-5793(99)00723-1
Abstract
The interaction of recombinant house fly (Musca domestica) P450 reductase with NADPH and the role of the FMN semiquinone in reducing cytochrome c have been investigated. House fly P450 reductase can rapidly oxidize only one molecule of NADPH, whereas the rate of oxidation of a second molecule of NADPH is too slow to account for the observed rates of catalysis. This demonstrates that house fly P450 reductase does not require a priming reaction with NADPH for catalysis. Kinetics of cytochrome c reduction and EPR spectroscopy revealed that the enzyme forms two types of neutral FMN semiquinone. One serves as the catalytic intermediate of cytochrome c reduction, and another one is an ‘air‐stable’ semiquinone, which reduces cytochrome c 3000 times more slowly. The results show that the reduction state of the house fly P450 reductase during catalysis cycles in a 0‐2‐1‐0 sequence.Keywords
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