Resolution of the cytochrome P-450-containing omega-hydroxylation system of liver microsomes into three components

A Y Lu, K W Junk, M J Coon
1969 Journal of Biological Chemistry  
The enzyme system in liver microsomes which catalyzes the w-hydroxylation of fatty acids in the presence of molecular oxygen and a reduced pyridine nucleotide has been solubilized and resolved into fractions containing cytochrome P-450, a cytochrome P-450 reductase, and a heat-stable factor. The apparent K, values of TPNH and DPNH are 2.0 x 10m5 M and 6.3 X 10e4 M, respectively. As a further indication of the role of cytochrome P-450, w-hydroxylation is enhanced in microsomes prepared from
more » ... ls previously treated with phenobarbital and is inhibited in the presence of carbon monoxide, with partial reversal of the inhibition by exposure to light. The soluble preparation of cytochrome P-450 exhibits a carbon monoxide difference spectrum, an electron paramagnetic resonance spectrum, and substrate difference spectra similar to those previously attributed to the microsomebound form. The difference spectrum obtained in the presence of laurate, with a peak at about 388 rnp and a trough at 419 mp, is of the type given by hexobarbital rather than aniline. The K, of lam-ate, determined from difference spectra, is 6.3 x 10V4 M, and the Km, determined in the complete hydroxylation system, is 4.4 X lop5 M. The by guest on
pmid:4389465 fatcat:zaxmxmazubakrmwp7y2c3u5opy