Testosterone catalytic

Photoketone (118) has served as the key intermediate in a relatively simple transformation of 3-keto-10/ -steroids to 3-keto-lOa-isomers without the assistance of other functional groups suitably situated next to the ring junction—a task that appears difficult to attempt by other methods. Optimal yields of (118) are achieved by catalytic hydrogenation of the unsaturated ketone (175), the photoisomer of 1-dehydrotestosterone acetate (see section III-C). In this way, a 6-step conversion of 1-dehydrotestosterone acetate (174) to IOa-testosterone acetate (127 acetate) is achieved in good yield. ° ... 

Formal isomerization of the double bond of testosterone to the 1-position and methylation at the 2-position provides yet another anabolic/androgenic agent. Mannich condensation of the fully saturated androstane derivative 93 with formaldehyde and di-methylamine gives aminoketone 94. A/B-trans steroids normally enolize preferentially toward the 2-position, explaining the regiospecificity of this reaction. Catalytic reduction at elevated temperature affords the 2a-methyl isomer 95. It is not at all unlikely that the reaction proceeds via the 2-methylene intermediate. The observed stereochemistry is no doubt attributable to the fact that the product represents the more stable equatorial isomer. The initial product would be expected to be the p-isomer but this would experience a severe 1,3-diaxial non-bonded interaction and epimerize via the enol. Bromination of the ketone proceeds largely at the tertiary carbon adjacent to the carbonyl (96). Dehydrohalogenation... 

CYP3A4 has been expressed in human lymphoblasts (Crespi et al., 1991a). The expression level in this report was quite low. Recent modifications to the promoter for cDNA expression and coexpression of OR have led to a 40-fold increase in catalytic activity. The mean testosterone 6j8-hydroxylase activity in microsomes from h3A4/OR cells (cultured in the presence of dexamethasone to induce cytochrome P450 reductase activity) [1000 pmol/(mg min)] is comparable to the mean values observed in human liver microsomes [1070 pmol/(mg min) Yamazaki et al., 1993]. The turnover number for testosterone and CYP3A4 in the human lymphoblasts was 15/min for endogenous OR levels and increased to 44/min with OR coexpression. 

The title compound, (4a, 5a, 17/ )-4, 5-epoxy-[6,7-2H2]-3, 17-dihydroxyandrost-2-ene-2-carbonitrile, 78,9, has been found to be of benefit in the treatment of some forms of breast cancer9. It has been synthesized10 in 6 steps as shown in equation 4. The label has been introduced into 7 in the first reaction step by catalytic deuteriation of androsta-4,6-dien-3,17-dione, 8. Similarly, [4-14C]trilostane (sp. act. 95 pCi/g, r.p. >98%, 57% overall yield) has been prepared10,11 in four steps from [4-14C]testosterone, 9. 

Yamazaki H, Mimura M, Sugahara C, et al. Catalytic roles of rat and human cytochrome P450 2A enzymes in testosterone 7alpha- and coumarin 7-hydroxylations. Biochem Pharmacol 1994 48 1524—1527. 

Kenworthy et al. [45] proposed a model with three subsites in order to explain the binding of testosterone (TS) and diazepam (DZ). One site binds diazepam, another binds testosterone, and the third is capable of binding either diazepam or testosterone. They found that testosterone caused extensive activation of diazepam metabolism, whereas diazepam caused inhibition of testosterone metabolism. Diazepam is present in the inhibitor database used to obtain the pharmacophoric model and its inhibitory activity is well explained by the model (y-residual = 0.27 log units). The model with multiple binding sites proposed by Kenworthy helped to explain the results of the obtained pharmacophoric model if one considers that competition will occur in the catalytic site that can bind either DZ or TS and that... 

Carbon monoxide inhibited the 6/3-. la-, and 16a-hydroxylation of testosterone by rat liver microsomes to different extents. A C0/02 ratio of 0.5 inhibited the la-, 6/i-, and 16a-hydroxylation reactions by 14%, 25%, and 36%, respectively, and the ratio of C0/02 needed for 50% inhibition of testosterone hydroxylation in the 16a-, 6/3-, and 7a-positions was 0.93, 1.54, and 2.36, respectively (36,48). Studies on the photochemical action spectrum revealed that CO inhibition of the three hydroxylation reactions was maximally reversed by monochromatic light at 450 nm, but there were differences in the shape of the photochemical reactivation spectra for the 6/3-, la-, and 16a-hydroxylation reactions (36,48). The data from our laboratory summarized above and at the First International Symposium on Microsomes and Drug Oxidation in 1968 pointed to multiple cytochromes P450 with different catalytic activities that were under separate regulatory control (36,45,46), and we indicated that the actual number of cytochromes that participate in the multiple hydroxylation reactions must await the solubilization and purification of the microsomal system (36). The use of different inducers of liver microsomal monooxygenases caused selective increases in the concentration of specific cytochromes P450 in fiver microsomes that greatly facilitated the isolation and purification of these hemoproteins. 

Buhler, D.R., C.L. Miranda, M.C. Henderson, Y.H. Yang, S.J. Lee and J.L. Wang-Buhler. Effects of 17 beta-estradiol and testosterone on hepatic mRNA/protein levels and catalytic activities of CYP2M1, CYP2K1, and CYP3A27 in rainbow trout (Oncorhynchus mykiss). Toxicol. Appl. Pharmacol. 168 91-101, 2000. 

Metal systems prepared in this way have proved effective in reducing catalytic destruction of solute. For example, we have found it possible to chromatograph testosterone in amounts down to 5 X 10" g in nn all-metal system with a flame-ionization detector. 

Several routes applicable to the large scale conversion of testosterone into 4,5a-dihydrotestosterone have been investigated. The method of choice appears to be via catalytic reduction of a 17-acyloxy-3,3-ethylenedioxyandrost-5-ene. Platinum-catalysed hydrogenation of 19-acetoxy, hydroxy-, or methoxy-cholestan-3-ones affords higher proportions of 3a-alcohols than does the 19-unsubstituted steroid. Tritiation of 17)S-hydroxyandrosta-l,4-dien-3-one affords testosterone having a tritium ratio of 1 3.4 (a P) at C-1 and 1 1.4 at C-2 implying that reduction must proceed, in part, by 1,4-addition. ... 

Ala245Ser and AIa245Thr mutant enzymes, it appears as though the loss of catalytic activity in the mutant forms correlates with the loss or repositioning of Wat519 (ref [234]). Nonetheless, these mutants are still able to metabolize the substrate testosterone at different sites, implying that a very intricate hydrogenbonding interplay exists between substrate and enz)mie. 

The ovarian granulosa cell, in response to stimulation by follicle-stimulating hormone (FSH) from the anterior pituitary gland and through the catalytic activity of P450 aromatase, converts testosterone to estradiol, the predominant and most potent of the ovarian estrogens (see Fig. 34.23). Similarly, androstenedione is converted to estrone in the ovary, although the major site of estrone production from androstenedione occurs in extraovarian tissues, principally skeletal muscle and adipose tissue. 

Testosterone is an intermediate in the biosynthesis of oestradiol. The conversion, which involves three successive hydroxylations and the loss of a methyl group, is catalysed by the enzyme aromatase. Aromatase has three catalytic activities 19-hydroxylase, 19-hydroxysteroid dehydrogenase and... 

Deuterated testosterone has been used to probe the catalytic mechanism of P450 3A4 [1372] (Fig. 9.19). Abstraction of the 6[ hydrogen of testosterone is highly stereoselective, with the oxygen rebound also going only to the po-sitioa The use of both 6-deuterated and 6-triti-ated testosterone led to the conclusion that the 6y -hydroxylation step has a high intrinsic kinetic deuterium isotope effect, which is considerably attenuated in the steady state [1372]. The conclusion is that steps other than C-H bond breaking hmit rates of the steady-state reaction. 

The initial studies with heterologously expressed P450 3A43 (in E. coli) showed only low testosterone 6jff-hydroxylation activity (a marker for other 3A subfamily members) [1531], Agarwal et al. [1254] reported different catalytic specificity in alprazolam oxidation compared to P450 3A4 and a relatively high level of activity, con-... 

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