Purification of 20 alpha-hydroxysteroid oxidoreductase from bovine fetal erythrocytes

Formation and degradation of dihydrotestosterone by recombinant members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase family

The structures of cDNA clones encoding four members of the rat 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD) family were characterized. The rat type I, type II and the novel type IV are genuine NAD+/H-dependent 3 beta-HSD isoenzymes. On the other hand, the liver-specific type III protein is a specific 3-keto-reductase (3-KSR) that catalyzes the conversion of 5 alpha-androstane-3-one-17 beta-ol (DHT) and 5 alpha-androstane 3,17-dione (A-dione) into their 3 beta-hydroxy metabolites. The aim of the present study was to further characterize the enzymatic properties of rat types I, III and IV, especially their role in the formation and degradation of DHT after transient expression in intact human HeLa cervical carcinoma, JEG-3 choriocarcinoma or SW-13 adrenal cortex adenocarcinoma cells in culture. The expressed type III 3-KSR in intact HeLa cells catalyzed the reduction of DHT into 3 beta-diol, whereas expression of type I 3 beta-HSD in these cell lines had no significant effect on the basal conversion of DHT into 3 beta-diol, but it did increase the formation of DHT from 3 beta-diol. A-dione is the predominant product obtained when DHT and 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol) are used as substrates in intact JEG-3 and SW-13 cells transfected with rat type I 3 beta-HSD. Furthermore, this predominant 17 beta-HSD activity was also observed in SW-13 cells transfected with the novel rat type IV 3 beta-HSD. The predominance of this 'secondary' 17 beta-HSD activity is also reflected in HeLa cells transfected with type I 3 beta-HSD by the deduced predominant pathway 3 beta-diol-->DHT-->5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol)-->androsterone (ADT), in which formation of 3 alpha-HSD activity of HeLa cells, whereas the other reactions are catalyzed by the type I 3 beta-HSD isoenzyme. This observation thus demonstrates that rat type I 3 beta-HSD may also catalyze the conversion of 3 alpha-diol into ADT through its intrinsic 17 beta-HSD activity. The predominant metabolic pathways observed in the present study could be attributed to preponderant bioavailability of NAD+ and NADPH in the intact transfected cells used.

3 alpha-hydroxysteroid dehydrogenase activity catalyzed by purified pig adrenal 20 alpha-hydroxysteroid dehydrogenase

In earlier studies, two distinct molecules, 20 alpha-HSD-I and 20 alpha-HSD-II, responsible for 20 alpha-HSD activity of pig adrenal cytosol were purified to homogeneity and characterized [S. Nakajin et al., J. Steroid Biochem. 33 (1989) 1181-1189]. We report here that the purified 20 alpha-HSD-I, which mainly catalyzes the reduction of 17 alpha-hydroxyprogesterone to 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, catalyzes 3 alpha-hydroxysteroid oxidoreductase activity for 5 alpha (or 5 beta)-androstanes (C19), 5 alpha (or 5 beta)-pregnanes (C21) in the presence of NADPH as the preferred cofactor. The purified enzyme has a preference for the 5 alpha (or 5 beta)-androstane substrates rather than 5 alpha (or 5 beta)-pregnane substrates, and the 5 beta-isomers rather than 5 alpha-isomers, respectively. Kinetic constants in the reduction for 5 alpha-androstanedione (Km; 3.3 microM, Vmax; 69.7 nmol/min/mg) and 5 beta-androstanedione (Km; 7.7 microM, Vmax; 135.7 nmol/min/mg) were demonstrated for comparison with those for 17 alpha-hydroxyprogesterone (Km; 26.2 microM, Vmax; 1.3 nmol/min/mg) which is a substrate for 20 alpha-HSD activity. Regarding oxidation, the apparent Km and Vmax values for 3 alpha-hydroxy-5 alpha-androstan-17-one were 1.7 microM and 43.2 nmol/min/mg, and 1.2 microM and 32.1 nmol/min/mg for 3 alpha-hydroxy-5 beta-androstan-17-one, respectively. 20 alpha-HSD activity in the reduction of 17 alpha-hydroxyprogesterone catalyzed by the purified enzyme was inhibited competitively by addition of 5 alpha-DHT with a Ki value of 2.0 microM. Furthermore, 17 alpha-hydroxyprogesterone inhibited competitively 3 alpha-HSD activity with a Ki value of 150 microM.

Purification and characterization of rat ovarian 20 alpha-hydroxysteroid dehydrogenase

To investigate the regulatory mechanism of 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) (EC 1.1.1.149) activity in ovarian tissue, the enzyme was purified from ovaries of normal mature female rats. Column chromatography of the cytosolic fraction from ovaries on DEAE-Toyopearl 650M revealed two peaks of the 20 alpha-HSD activity at different ionic strengths. These peaks were designated HSD1 and HSD2, respectively. Each of the active fractions was further purified to homogeneity by dye-affinity chromatography using Matrex Green A and AF Red-Toyopearl. Both the fractions appeared as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (at Mr = 33,000 under reducing conditions). Under non-reducing conditions, similar values were obtained on gel-exclusion HPLC, indicating that the enzyme fractions were single-stranded, monomeric polypeptides. Homogeneous HSD1 and HSD2 were purified 361-fold and 509-fold, respectively, and differed in their substrate preference. The two enzyme fractions had Km values of 4.75 microM and 5.16 microM for 20 alpha-dihydroprogesterone, respectively, and showed almost the same RF values on reverse-phase HPLC and free-zone capillary electrophoresis. However, amino acid composition was slightly different, i.e. lysin content was higher in HSD1 than HSD2. Thus, it was clarified that two types of 20 alpha-HSD with very similar molecular structures are present in the rat ovary.

Fetal lamb 3 beta, 20 alpha-hydroxysteroid oxidoreductase: dual activity at the same active site examined by affinity labeling with 16 alpha-(bromo[2'-14C]acetoxy)progesterone

3 beta,20 alpha-Hydroxysteroid oxidoreductase was purified to homogeneity from fetal lamb erythrocytes. The Mr 35,000 enzyme utilizes NADPH and reduces progesterone to 4-pregnen-20 alpha-ol-3-one [Km = 30.8 microM and Vmax = 0.7 nmol min-1 (nmol of enzyme)-1] and 5 alpha-dihydrotestosterone to 5 alpha-androstane-3 beta, 17 beta-diol [Km = 74 microM and Vmax = 1.3 nmol min-1 (nmol of enzyme)-1]. 5 alpha-Dihydrotestosterone competitively inhibits (Ki = 102 microM) 20 alpha-reductase activity, suggesting that both substrates may be reduced at the same active site. 16 alpha-(Bromoacetoxy)progesterone competitively inhibits 3 beta- and 20 alpha-reductase activities and also causes time-dependent and irreversible losses of both 3 beta-reductase and 20 alpha-reductase activities with the same pseudo-first order kinetic t1/2 value of 75 min. Progesterone and 5 alpha-dihydrotestosterone protect the enzyme against loss of the two reductase activities presumably by competing with the affinity alkylating steroid for the active site of 3 beta,20 alpha-hydroxysteroid oxidoreductase. 16 alpha-(Bromo[2'-14C]acetoxy) progesterone radiolabels the active site of 3 beta,20 alpha-hydroxysteroid oxidoreductase wherein 1 mol of steroid completely inactivates 1 mol of enzyme with complete loss of both reductase activities. Hydrolysis of the 14C-labeled enzyme with 6 N HCl at 110 degrees C and analysis of the amino acid hydrolysate identified predominantly N pi-(carboxy[2'-14C]methyl)histidine [His(pi-CM)].(ABSTRACT TRUNCATED AT 250 WORDS)

Purification and characterization of a novel form of 20 alpha-hydroxysteroid dehydrogenase from Clostridium scindens

We have purified a steroid-inducible 20 alpha-hydroxysteroid dehydrogenase from Clostridium scindens to apparent homogeneity. The final enzyme preparation was purified 252-fold, with a recovery of 14%. Denaturing and nondenaturing polyacrylamide gradient gel electrophoresis showed that the native enzyme (Mr, 162,000) was a tetramer composed of subunits with a molecular weight of 40,000. The isoelectric point was approximately pH 6.1. The purified enzyme was highly specific for adrenocorticosteroid substrates possessing 17 alpha, 21-dihydroxy groups. The purified enzyme had high specific activity for the reduction of cortisone (Vmax, 280 nmol/min per mg of protein; Km, 22 microM) but was less reactive with cortisol (Vmax, 120 nmol/min per mg of protein; Km, 32 microM) at pH 6.3. The apparent Km for NADH was 8.1 microM with cortisone (50 microM) as the cosubstrate. Substrate inhibition was observed with concentrations of NADH greater than 0.1 mM. The purified enzyme also catalyzed the oxidation of 20 alpha-dihydrocortisol (Vmax, 200 nmol/min per mg of protein; Km, 41 microM) at pH 7.9. The apparent Km for NAD+ was 526 microM. The initial reaction velocities with NADPH were less than 50% of those with NADH. The amino-terminal sequence was determined to be Ala-Val-Lys-Val-Ala-Ile-Asn-Gly-Phe-Gly-Arg. These results indicate that this enzyme is a novel form of 20 alpha-hydroxysteroid dehydrogenase.

Cofactor requirements of steroid-17-20-desmolase and 20 alpha-hydroxysteroid dehydrogenase activities in cell extracts of Clostridium scindens

Two neutral steroid-transforming activities were demonstrated in cell extracts of Clostridium scindens. Steroid-17-20-desmolase and 20 alpha-hydroxysteroid dehydrogenase were found to be inducible in cells cultured in the presence of cortisol. Both activities required manganese ions and NAD+ or NADH for activity. Cortisol, cortisone and 11-desoxycortisol were substrates as well as inducers of steroid-17-20-desmolase and 20 alpha-hydroxysteroid dehydrogenase activities. 17 alpha-Hydroxyprogesterone was an effective inducer but did not serve as a substrate for either enzyme activity. C. scindens is the first bacterial species of the normal human intestinal flora reported to elaborate inducible steroid-17-20-desmolase and 20 alpha-hydroxysteroid dehydrogenase activities. The results of cofactor, substrate specificity and induction studies suggest that these two activities may reside in the same enzyme complex.

Isolation of 3 beta,20 alpha-hydroxysteroid oxidoreductase from sheep fetal blood

3 beta,20 alpha-Hydroxysteroid oxidoreductase has been isolated from ovine fetal blood by a 2,370-fold purification scheme of ammonium sulfate fractionation, calcium phosphate gel adsorption, affinity chromatography, and fast performance liquid chromatography. A new high performance liquid chromatography-based assay for measuring 20 alpha-reductase activity is described. The enzyme is a monomer with a molecular weight of 35,000 and uses NADPH as a cofactor for reductase activity. It reduces progesterone to 4-pregnen-20 alpha-ol-3-one or 5 alpha-dihydrotestosterone to 5 alpha-androstan-3 beta,17 beta-diol with kinetic characteristics of Km = 30.8 microM and Vmax = 0.7 nmol min-1 (nmol of enzyme)-1 or Km = 74 microM and Vmax = 1.3 nmol min-1 (nmol of enzyme)-1, respectively. 5 alpha-Dihydrotestosterone competitively inhibits 20 alpha-reductase activity with a Ki value of 102 microM.

Purification and characterization of 20 alpha-hydroxysteroid dehydrogenase from bull testis

20 alpha-Hydroxysteroid dehydrogenase (20 alpha-HSD) from bull testis has been purified to homogeneity and characterized in terms of apparent molecular weight, lack of subunit composition, substrate and cofactor specificity and certain kinetic parameters. The enzyme activity is localized in the 105,000 g supernatant and is stable at 4 degrees C in the presence of glycerol and dithiothreitol. Purification was achieved by ammonium sulfate precipitation followed by affinity chromatography on reactive red 120-agarose and subsequent gel filtration. The apparent molecular weight of the homogeneous enzyme, as determined by gel filtration on Sephacryl S-300 is 34,000. The mobility of the enzyme in sodium dodecyl sulfate (SDS) gel electrophoresis corresponds to a mol. wt of 40,000. These observations indicate that the enzyme is a single-stranded, monomeric polypeptide. The enzyme catalyzes the reduction of the 17-hydroxyprogesterone to 17,20 alpha-dihydroxy-4-pregnene-3-one in the presence of NADPH, the preferred cofactor. Homogeneous 20 alpha-HSD has an SA of 115 mIU/mg, and has been purified 14,000-fold with an overall 68% recovery. It exhibits a pH optimum at 5.6 and appears to be highly specific for 17-hydroxyprogesterone with an apparent Km-value of 7.3 X 10(-5) M. Androstenedione and corticosterone do not serve as substrates under the described experimental conditions. The enzyme does not possess 17 alpha- or 17 beta-HSD activity.

Studies of the coenzyme binding site of rat ovarian 20 alpha-hydroxysteroid dehydrogenase

Rat ovarian 20 alpha-hydroxysteroid dehydrogenase was shown to be effectively inhibited by adenosine derivatives, nicotinamide derivatives, NADP analogs, N-alkylammonium chlorides, and carboxylic acids through coenzyme-competitive inhibition studies. Multiple inhibition analysis was used to demonstrate either simultaneous binding of inhibitors that interact with different regions of the NADP-binding site or mutual exclusion of inhibitors that interact with the same region on the enzyme. The results of these studies demonstrated that the 2'-phosphate, the pyrophosphate, and the positively charged ring nitrogen are important features of the coenzyme structure in binding to the coenzyme-binding site of the enzyme. In addition, the presence of a hydrophobic region near the NADP-binding site was indicated by positive chainlength effects observed in the binding of nicotinamide derivatives, alkylammonium chlorides, and carboxylic acids.

The effect of progesterone on hemoglobin synthesis in suspension cultures of fetal erythroid cells from calf liver

When fetal calf liver erythroid cells were incubated in the presence of small amounts of progesterone (10(-7)-10(-8) M), the hemoglobin synthesis in these cells was significantly increased. The increase in the amount of radioactivity in de novo synthesized hemoglobins could be demonstrated when techniques such as isoelectric focusing, chromatography on DEAE-cellulose and gel chromatography on Sephadex G-100 were used to isolate the hemoglobin fraction. Using the latter technique, it was shown that the synthesis of cytoplasmic non-hemoglobin proteins in erythroid-cell lysates was also stimulated by progesterone. The presence of hepatocytes in culture nullified the hormone action. It was necessary that progesterone was present during the first hours of culture. Delayed addition of the steroid to the cells had no effect on hemoglobin synthesis. Erythropoietin was necessary to obtain stimulation by progesterone. These results suggest that the target cell of the hormone is an erythropoietin-sensitive cell. High concentrations of progesterone (10(-4) M) strongly inhibited hemoglobin synthesis in fetal calf erythroid cells. Culture of cells under this condition, however, gives rise to a cell population that preferentially synthesizes adult hemoglobin. Our results suggest that in the erythropoietic calf liver, high concentrations of progesterone may preferentially stimulate adult hemoglobin synthesis, or that those cells which have a high capacity to synthesize adult hemoglobins are less sensitive to toxic concentrations of the hormone. The effects of stimulation of hemoglobin synthesis in fetal calf erythroid cells occur at hormone concentrations that suggest a possible physiological role of progesterone in fetal, and eventually also in maternal, erythropoiesis.