63-00-3Relevant articles and documents
Escherichia coli expression of site-directed mutants of cytochrome P450 2B1 from six substrate recognition sites: Substrate specificity and inhibitor selectivity studies
You Qun He,You Ai He,Halpert
, p. 574 - 579 (1995)
Cytochrome P450 2B1 wild-type and eight site-directed mutations at positions 114, 206, 236, 302, 363, 367, and 478 have been expressed in an Escherichia coli system. Solubilized membrane preparations yielded 100-180 nmol of P450/L of culture. The metabolism of a number of substrates including androstenedione, progesterone, (benzyloxy)resorufin, pentoxyresorufin, and benzphetamine was analyzed. The E. coli-expressed enzymes displayed the same androstenedione metabolite profiles previously observed with a COS cell expression system. Several of the mutants exhibited an increased rate of progesterone hydroxylation, possibly as the result of an enlarged substrate binding pocket and increased D-ring α-face binding. (Benzyloxy)resorufin and pentoxyresorufin O-dealkylation by the P450 2B1 mutants exhibited activities ranging from 10% to 99% and 3% to 71% of wild-type, respectively. Interestingly, the Val-363 → Leu mutant showed markedly suppressed pentoxyresorufin but unaltered (benzyloxy)resorufin dealkylase activity. Benzphetamine N-demethylase activities ranged from 28% to 110% of wildtype. Mechanism-based inactivation of the P450 2B1 mutants showed that susceptibility to inactivation by chloramphenicol and D-erythro- and L- threo-chloramphenicol was abolished in the Val-367 → Ala mutant. The Val- 363 → Leu mutant was refractory to L-threo-chloramphenicol. Studies of chloramphenicol covalent binding and metabolism by the Val-367 → Ala mutant showed that its resistance to inactivation is largely attributable to an inability to bioactivate the inhibitor. The expression of P450 2B1 wild-type and mutants in E. coli provides an excellent opportunity to study structure/function relationships by site-directed mutagenesis.
Oxidative Diversification of Steroids by Nature-Inspired Scanning Glycine Mutagenesis of P450BM3 (CYP102A1)
Cao, Yang,Chen, Wenyu,Fisher, Matthew J.,Leung, Aaron,Wong, Luet L.
, p. 8334 - 8343 (2020/09/18)
Steroidal compounds are some of the most prescribed medicines, being indicated for the treatment of a variety of conditions including inflammation, heart disease, and cancer. Synthetic approaches to functionalized steroids are important for generating steroidal agents for drug screening and development. However, chemical activation is challenging because of the predominance of inert, aliphatic C-H bonds in steroids. Here, we report the engineering of the stable, highly active bacterial cytochrome P450 enzyme P450BM3 (CYP102A1) from Bacillus megaterium for the mono- and dihydroxylation of androstenedione (AD), dehydroepiandrosterone (DHEA), and testosterone (TST). In order to design altered steroid binding orientations, we compared the structure of wild type P450BM3 with the steroid C19-demethylase CYP19A1 with AD bound within its active site and identified regions of the I helix and the β4 strand that blocked this binding orientation in P450BM3. Scanning glycine mutagenesis across 11 residues in these two regions led to steroid oxidation products not previously reported for P450BM3. Combining these glycine mutations in a second round of mutagenesis led to a small library of P450BM3 variants capable of selective (up to 97%) oxidation of AD, DHEA, and TST at the widest range of positions (C1, C2, C6, C7, C15, and C16) by a bacterial P450 enzyme. Computational docking of these steroids into molecular dynamics simulated structures of selective P450BM3 variants suggested crucial roles of glycine mutations in enabling different binding orientations from the wild type, including one that closely resembled that of AD in CYP19A1, while other mutations fine-tuned the product selectivity. This approach of designing mutations by taking inspiration from nature can be applied to other substrates and enzymes for the synthesis of natural products and their derivatives.
Preparative-Scale Production of Testosterone Metabolites by Human Liver Cytochrome P450 Enzyme 3A4
Fessner, Nico D.,Srdi?, Matic,Weber, Hansj?rg,Schmid, Christian,Sch?nauer, David,Schwaneberg, Ulrich,Glieder, Anton
, p. 2725 - 2738 (2020/06/03)
Just like the drugs themselves, their metabolites have to be evaluated to succeed in a drug development and approval process. It is therefore essential to be able to predict drug metabolism and to synthesise sufficient metabolite quantities for further pharmacological testing. This study evaluates the possibility of using in vitro biotransformations to solve both these challenges in the case of testosterone as a representative component for steroids. The application of cells of Pichia pastoris with expressed membrane-associated human liver cytochrome P450 enzyme (P450) 3A4 in two cycles of a preparative-scale bioreactor experiment enabled the isolation of the common metabolites 6β-hydroxytestosterone and 6β-hydroxyandrostenedione on a 100 mg scale. Side-product formation caused by enzymes intrinsic to P. pastoris was reduced. In addition more polar testosterone metabolites formed by a P450 3A4-catalysed bioconversion, than the known mono-hydroxylated ones, are reported and 6-dehydro-15β-hydroxytestosterone as well as the di-hydroxylated steroids 6β,16β-dihydroxytestosterone, 6β,17β-dihydroxy-4-androstene-3,16-dione and 6β,12β-dihydroxyandrostenedione were isolated and verified by NMR analysis. Their respective biological significance remains to be investigated. Whole-cell P450 catalysts expressed in P. pastoris qualify as a tool for the preparative-scale synthesis of human metabolites. Biotransformation processes in combination with standard chemical procedures allow the isolation and characterisation even of minor drug metabolite products. (Figure presented.).
