Thermodynamic Properties of Oxidation-Reduction Reactions of Bacterial, Microsomal, and Mitochondrial Cytochromes P-450: An Entropy-Enthalpy Compensation Effect

Yung Yuan Huang, Takayuki Hara, Stephan Sligar, Minor J. Coon, Tokuji Kimura

Research output: Contribution to journalArticlepeer-review

Abstract

An optically transparent thin-layer electrode cell with a very small volume was used for de- termination of the formal reduction potentials of bacterial, microsomal, and mitochondrial cytochromes P-450. At an extrapolated zero concentration of dye, the bacterial cytochrome from Pseudomonas putida catalyzing the hydroxylation of camphor and the adrenal mitochondrial cytochrome catalyzing the cholesterol side-chain cleavage reaction had formal reduction potentials of-168 and -285 mV (pH 7.5 and 25 °C), respectively. The oxidation-reduction potentials for the rabbit liver microsomal cytochrome P-450 induced by 3-methylcholanthrene and the mitochondrial cytochrome for steroid 11β-hydroxylation were found as -360 and -286 mV, respectively. Potential measurements at different temperatures allowed documentation of the standard thermodynamic parameters for cytochrome P-450 reduction for the first time. All cytochromes tested were found to have a relatively large negative entropy change upon reduction. The extent of these changes is comparable to that observed for the ferric-ferrous couple of cytochrome c. An entropy-enthalpy compensation effect was observed among the four cytochromes P-450 examined although the correlation is weaker than that observed with cytochrome c isolated from various sources.

Original languageEnglish (US)
Pages (from-to)1390-1394
Number of pages5
JournalBiochemistry
Volume25
Issue number6
DOIs
StatePublished - 1986
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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