Characterization of high-H2O2-tolerant bacterial cytochrome P450 CYP105D18: insights into papaverine N-oxidation

Structural determination and characterisation of the CYP105Q4 cytochrome P450 enzyme from Mycobacterium marinum

The cytochrome P450 family of heme metalloenzymes (CYPs) catalyse important biological monooxygenation reactions. Mycobacterium marinum contains a gene encoding a CYP105Q4 enzyme of unknown function. Other members of the CYP105 CYP family have key roles in bacterial metabolism including the synthesis of secondary metabolites. We produced and purified the cytochrome P450 enzyme CYP105Q4 to enable its characterization. Several nitrogen-donor atom-containing ligands were found to bind to CYP105Q4 generating type II changes in the UV-vis absorbance spectrum. Based on the UV-vis absorbance spectra none of the potential substrate ligands we tested with CYP105Q4 were able to displace the sixth distal aqua ligand from the heme, though there was evidence for binding of oleic acid and amphotericin B. The crystal structure of CYP105Q4 in the substrate-free form was determined in an open conformation. A computational structural similarity search (Dali) was used to find the most closely related characterized relatives within the CYP105 family. The structure of CYP105Q4 enzyme was compared to the GfsF CYP enzyme from Streptomyces graminofaciens which is involved in the biosynthesis of a macrolide polyketide. This structural comparison to GfsF revealed conformational changes in the helices and loops near the entrance to the substrate access channel. A disordered B/C loop region, usually involved in substrate recognition, was also observed.

Microbial P450 repertoire (P450ome) and its application feasibility in pharmaceutical industry, chemical industry, and environmental protection

Cytochrome P450s (CYPs) are heme-thiolated enzymes that catalyze the oxidation of C-H bonds in a regio- and stereo-selective manner. CYPs are widely present in the biological world. With the completion of more biological genome sequencing, the number and types of P450 enzymes have increased rapidly. P450 in microorganisms is easy to clone and express, rich in catalytic types, and strong in substrate adaptability, which has good application potential. Although the number of P450 enzymes found in microorganisms is huge, the function of most of the microorganism P450s has not been studied, and it contains a large number of excellent biocatalysts to be developed. This review is based on the P450 groups in microorganisms. First, it reviews the distribution of P450 groups in different microbial species, and then studies the application of microbial P450 enzymes in the pharmaceutical industry, chemical industry and environmental pollutant treatment in recent years. And focused on the application fields of P450 enzymes of different families to guide the selection of suitable P450s from the huge P450 library. In view of the current shortcomings of microbial P450 in the application process, the final solution is the most likely to assist the application of P450 enzymes in large-scale, that is, whole cell transformation combined with engineering, fusion P450 combined with immobilization technology.

Analysis of critical residues for peroxygenation and improved peroxygenase activity via in situ H2O2 generation in CYP105D18

Limited numbers of CYPs have been reported to work naturally as peroxygenases. The peroxide shunt pathway can be efficiently used as an alternative for the NAD(P)H and reductase systems, particularly in high hydrogen peroxide (H2O2) resistance CYPs. We reported the structural and biochemical features of CYP105D18 peroxygenase for its high H2O2 tolerance capacity. Q348 was a crucial residue for the stability of CYP105D18 during the exposure to H2O2. In addition, the role of the hydrophilic amino acid T239 from the I helix for peroxygenation and regiospecificity toward testosterone was investigated. Interestingly, T239E differs in product formation from wild type, catalyzing testosterone to androstenedione in the presence of H2O2. The other variant, T239A, worked with the Pdx/Pdr system and was unable to catalyze testosterone conversion in the presence of H2O2, suggesting the transformation of peroxygenase into monooxygenase. CYP105D18 supported the alternative method of H2O2 used for the catalysis of testosterone. The use of the same concentration of urea hydrogen peroxide adducts in place of direct H2O2 was more efficient for 2β-hydroxytestosterone conversion. Furthermore, in situ H2O2 generation using GOx/glucose system enhanced the catalytic efficiency (kcat/Km) for wild type and F184A by 1.3- and 1.9-fold, respectively, compared to direct use of H2O2 The engineering of CYP105D18, its improved peroxygenase activity, and alteration in the product oxidation facilitate CYP105D18 as a potential candidate for biotechnological applications.

H2O2-Driven Hydroxylation of Steroids Catalyzed by Cytochrome P450 CYP105D18: Exploration of the Substrate Access Channel

CYP105D18 supports H2O2 as an oxygen surrogate for catalysis well and shows high H2O2 resistance capacity. We report the hydroxylation of different steroids using H2O2 as a cosubstrate. Testosterone was regiospecifically hydroxylated to 2β-hydroxytestosterone. Based on the experimental data and molecular docking, we predicted that hydroxylation of methyl testosterone and nandrolone would occur at position 2 in the A-ring, while hydroxylation of androstenedione and adrenosterone was predicted to occur in the B-ring. Further, structure-guided rational design of the substrate access channel was performed with the mutagenesis of residues S63, R82, and F184. Among the mutants, S63A showed a marked decrease in product formation, while F184A showed a significant increase in product formation in testosterone, nandrolone, methyl testosterone, androstenedione, and adrenosterone. The catalytic efficiency (kcat/Km) toward testosterone was increased 1.36-fold in the F184A mutant over that in the wild-type enzyme. These findings might facilitate the potential use of CYP105D18 and further engineering to establish the basis of biotechnological applications. IMPORTANCE The structural modification of steroids is a challenging chemical reaction. Modifying the core ring and the side chain improves the biological activity of steroids. In particular, bacterial cytochrome P450s are used as promiscuous enzymes for the activation of nonreactive carbons of steroids. In the present work, we reported the H2O2-mediated hydroxylation of steroids by CYP105D18, which also overcomes the use of expensive cofactors. Further, exploring the substrate access channel and modifying the bulky amino acid F184A increase substrate conversion while modifying the substrate recognizing amino acid S63 markedly decreases product formation. Exploring the substrate access channel and the rational design of CYP105D18 can improve the substrate conversion, which facilitates the engineering of P450s for industrial application.