Purification from adult pig testicular P-450 and 17 alpha-hydroxylase activity of P-450 containing liposomal membranes

Non-steroidal CYP17A1 Inhibitors: Discovery and Assessment

CYP17A1 is an enzyme that plays a major role in steroidogenesis and is critically involved in the biosynthesis of steroid hormones. Therefore, it remains an attractive target in several serious hormone-dependent cancer diseases, such as prostate cancer and breast cancer. The medicinal chemistry community has been committed to the discovery and development of CYP17A1 inhibitors for many years, particularly for the treatment of castration-resistant prostate cancer. The current Perspective reflects upon the discovery and evaluation of non-steroidal CYP17A1 inhibitors from a medicinal chemistry angle. Emphasis is placed on the structural aspects of the target, key learnings from the presented chemotypes, and design guidelines for future inhibitors.

Purification of cytochromes P-450(scc) and P-450(17 alpha) by steroid-binding affinity column chromatography

The preparation, testing and use of a variety of cholesterol-, deoxycorticosterone (DOC)- and pregnenolone-binding 1,6-diaminohexyl (EAH)-Sepharose 4B supports for affinity column chromatography of cytochromes P-450(scc) and P-450(17 alpha) from bovine adrenal and pig testis are described. EAH-Sepharose 4B has free amino groups at the end of a 10-atom spacer arm. Hydroxyl groups of cholesterol (3 beta), deoxycorticosterone (21 beta) and pregnenolone (3 beta) are linked to succinic anhydride in pyridine through an ester linkage. These coupling ligands of hemisuccinate were synthesized by a general procedure. Free amino groups of EAH-Sepharose 4B were used to couple ligands, containing carboxyl groups, by the carbodiimide coupling method. Both the purified cytochromes P-450(scc) and P-450(17 alpha) were found to be homogeneous and estimated to have a molecular weight of 52,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The carbon monoxide difference spectra with peaks at 450 and 448 nm exhibit the absorption spectra of typical cytochromes P-450(scc) and P-450(17 alpha), respectively. Cytochromes P-450(scc) and P-450(17 alpha) were determined to have isoelectric points of 8.0 and 6.5 in isoelectric focusing on a pH gradient gel. Cytochrome P-450s can be purified between 425- and 1000-fold from the crude extracts.

A simplified procedure for purification of cytochrome P-450 by preparative ampholine gel for isoelectric focusing

The purification process for cytochrome P450 is very complicated, involving five or more column chromatography steps for the final preparation. This paper describes a reduction in the number of the steps; it can be easily purified from pig testis microsomes with improved the yield. As the first step, DEAE-Toyopearl column chromatography is performed only once and then, as the second step, the partially purified cytochrome P450 is completely purified by a preparative Ampholine PAG-plate Gel for Isoelectric Focusing. The combination reduced the purification to a two-step procedure.

A two-step purification of cytochrome P-450 from adult pig testis by pregnenolone affinity column chromatography

Adult testicular cytochrome P-450 was purified by a two-step procedure utilizing hydroxylapatite and pregnenolone affinity column chromatography. The cytochrome P-450 was determined to have an isoelectric point of 6.43 on analytical isoelectric focusing. The purified cytochrome P-450 was found to be homogeneous and its molecular weight was estimated to be 52,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The carbon monoxide difference spectrum with a peak at 448 nm exhibited the absorption spectrum of a typical cytochrome P-450. A purification of 755x was achieved with a yield of 3.09%.

Purification of cytochrome P-450 from adult pig testis by hydroxylapatite and deoxycorticosterone affinity column chromatography

Adult testicular cytochrome P-450 was purified by a two-step procedure utilizing hydroxylapatite and deoxycorticosterone affinity column chromatography. Cytochrome P-450 was determined to have an isoelectric point of 6.5 on analytical isoelectric focusing. The purified cytochrome P-450 was found to be homogeneous and its molecular mass was estimated to be 52000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The carbon monoxide difference spectrum with a peak at 448 nm exhibited the absorption spectrum of a typical cytochrome P-450. A 1000-fold purification was achieved with a yield of 5%.

Two-step purification of cytochrome P-450 from adult pig testis by isoelectric focusing

Adult testicular cytochrome P-450 was purified by a two-step procedure utilizing preparative isoelectrofocusing. Purification was achieved 1132 times with a yield of 4.82%. 17alpha-hydroxylase activity was shown to be 14.5 nmol of product/min/nmol of P-450. The cytochrome P-450 was determined to have an isoelectric point of 6.45 on analytical isoelectric focusing. The purified cytochrome P-450 was found to be homogeneous and its molecular weight was estimated to be 52000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The carbon monoxide difference spectrum with a peak at 448 nm exhibited the absorption spectrum of a typical cytochrome P-450.

Purification of cytochrome b5 from pig testis microsomes by isoelectric focusing in an immobiline pH gradient

Testicular cytochrome b5 was purified by a procedure including preparative isoelectrofocusing. The cytochrome b5 was determined to have an isoelectric point of 4.45 on analytical isoelectric focusing. The purified cytochrome b5 was found to be homogeneous and its molecular weight was estimated to be 16,000 on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The oxidized and reduced forms of the purified preparation exhibited absorption spectra of a typical cytochrome b5. A 69-fold purification was achieved with an overall yield of 6.2%. Following preparation of the microsomes, the purification is accomplished by a two-step procedure utilizing column chromatography and preparative isoelectric focusing.

Effect of phospholipids and organic solvents on the formation of 5,16-androstadien-3 beta-ol from pregnenolone in adrenal and testicular microsomes

The formation of 5,16-androstadien-3 beta-ol from pregnenolone (andien-beta synthase activity) is catalyzed by cytochrome P450c17, which also catalyzes C-17-hydroxy/lyase activity in the biosynthesis of androgens. Andien-beta synthase is very active in porcine Leydig cells, but it is almost undetectable in porcine and bovine adrenal, although the adrenal gland also expresses P450c17. We have treated microsomal preparations with lipids and organic solvents to examine if the andien-beta synthase and C-17-hydroxy/lyase activities of P450c17 were affected by these agents. The addition of some phospholipids to the microsomal preparations inhibited both P450c17 activities. Phospholipids with different fatty acids had no effect on the ratio of andien-beta synthase to C-17-hydroxy/lyase activity. The addition of solvents to the microsomal preparations generally inhibited both P450c17 activities. However, the addition of acetyl acetone up to 5% (v/v) preferentially increased the andien-beta synthase activity while decreasing, the C-17-hydroxy/lyase activity. The effect was dose-dependent, specific to acetyl acetone and was seen in both testis and adrenal microsomes. The exact nature of the stimulation of andien-beta synthase activity is unknown, but the andien-beta synthase activity obtained after treatment with acetyl acetone was directly correlated to total P450c17 activity in the untreated microsomes. The inhibition of C-17-hydroxy/lyase activity by acetyl acetone was particularly apparent with the C-17,20-lyase reaction rather than the 17 alpha-hydroxylase reaction. The addition of acetyl acetone can potentially be used to assess the total potential of P450c17 to catalyze andien-beta synthase activity in vitro.