Cytochrome P-450 in liver microsomes of streptozotocin-induced diabetic rats: purification and characterization

Abstract Two diabetes-inducible forms of cytochrome P -450, named P -450ST-1 and -ST-2, were purified from the liver microsomes of streptozotocin-diabetic male rats by sodium cholate solubilization, octylamino-Sepharose 4B chromatography and high-performance liquid chromatography with DEAE-5PW and hydroxyapatite columns. The purified P -450 forms gave a single band each on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular weight of 48500 for P -450ST-1 or 48000 for P -450ST-2. The Co-reduced spectral maxima of P -450ST-1 and -ST-2 were at 451 nm. The two cytochromes had the low-spin state of heme in the oxidized form. Both P -450ST-1 and -ST-2 catalyzed the metabolism of aniline, benzphetamine, p -nitroanisole, testosterone and aminopyrine. However, the catalytic activity of P -450ST-2 for these substrates was apparently higher than that of ST-1. Analyses of the NH 2 -terminal amino-acid sequence and Western immunoblot showed that P -450ST-1 and -ST-2 differed structurally from each other. The catalytic activities, molecular weights, NH 2 -terminal sequences and/or immunochemical properties of P -450ST-1 and -ST-2 did not agree with those of the other cytochrome P -450 forms purified from diabetic rats previously.