Heterogeneity of the bovine adrenal steroid 21-hydroxylase.
The results presented indicate that purified cytochrome P-45021 which migrated upon SDS gel electrophoresis essentially as a single band, is further separable into different species by ion-exchange chromatography. The P-450 eluted from the CM-Sephadex column at different points along the buffer concentration gradient, exhibited significant differences in (1) the 21-hydroxylation of 17 alpha-OH-progesterone compared to progesterone and (2) the Type I spectral change produced by 17 alpha-OH-progesterone compared to that due to delta 4-androstenedione. These results indicate that the purified P-450 which appeared homogeneous contains different species differing in net charge and steroid preferences for 21-hydroxylation and binding. The ratio, 21-hydroxylation of 17 alpha-OH-progesterone/progesterone ranged between 2.6 and 0.86 suggesting that the purified preparation is a mixture of 17 alpha-OH-progesterone preferring and progesterone preferring species. Possible molecular bases for the heterogeneity of the 21-hydroxylase are discussed.
Narasimhulu
S
S
Harrison Department for Surgical Research, School of Medicine, University of Pennsylvania, Philadelphia 19104.
D000302:Adrenal Cortex / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007527:Isoenzymes / Q000302:isolation & purification*; D008861:Microsomes / Q000201:enzymology; D013255:Steroid 21-Hydroxylase / Q000302:isolation & purification* / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000302:isolation & purification*
D007527:Isoenzymes; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase