Engineering Bacterial Cytochrome P450 (P450) BM3 into a Prototype with Human P450 Enzyme Activity Using Indigo Formation
作者:Sun-Ha Park、Dong-Hyun Kim、Dooil Kim、Dae-Hwan Kim、Heung-Chae Jung、Jae-Gu Pan、Taeho Ahn、Donghak Kim、Chul-Ho Yun
DOI:10.1124/dmd.109.030759
日期:2010.5
Human cytochrome P450 (P450) enzymes metabolize a variety of endogenous and xenobiotic compounds, including steroids, drugs, and environmental chemicals. In this study, we examine the possibility that bacterial P450 BM3 (CYP102A1) mutants with indole oxidation activity have the catalytic activities of human P450 enzymes. Error-prone polymerase chain reaction was carried out on the heme domain-coding region of the wild-type gene to generate a CYP102A1 DNA library. The library was transformed into Escherichia coli for expression of the P450 mutants. A colorimetric colony-based method was adopted for primary screening of the mutants. When the P450 activities were measured at the whole-cell level, some of the blue colonies, but not the white colonies, possessed apparent oxidation activity toward coumarin and 7-ethoxycoumarin, which are typical human P450 substrates that produce fluorescent products. Coumarin is oxidized by the CYP102A1 mutants to produce two metabolites, 7-hydroxycoumarin and 3-hydroxycoumarin. In addition, 7-ethoxycoumarin is simultaneously oxidized to 7-hydroxycoumarin by O -deethylation reaction and to 3-hydroxy,7-ethoxycoumarin by 3-hydroxylation reactions. Highly active mutants are also able to metabolize several other human P450 substrates, including phenacetin, ethoxyresorufin, and chlorzoxazone. These results indicate that indigo formation provides a simple assay for identifying CYP102A1 mutants with a greater potential for human P450 activity. Furthermore, our computational findings suggest a correlation between the stabilization of the binding site and the catalytic efficiency of CYP102A1 mutants toward coumarin: the more stable the structure in the binding site, the lower the energy barrier and the higher the catalytic efficiency.
人类细胞色素 P450(P450)酶可代谢多种内源性和异生物化合物,包括类固醇、药物和环境化学品。在本研究中,我们研究了具有吲哚氧化活性的细菌 P450 BM3(CYP102A1)突变体具有人类 P450 酶催化活性的可能性。对野生型基因的血红素结构域编码区进行易错聚合酶链反应,生成 CYP102A1 DNA 文库。该文库被转化到大肠杆菌中,用于表达 P450 突变体。突变体的初筛采用比色菌落法。在全细胞水平测量 P450 活性时,一些蓝色菌落(而非白色菌落)对香豆素和 7- 乙氧基香豆素具有明显的氧化活性,而香豆素和 7- 乙氧基香豆素是典型的人类 P450 底物,会产生荧光产物。香豆素被 CYP102A1 突变体氧化后会产生两种代谢物,即 7-羟基香豆素和 3-羟基香豆素。此外,7-乙氧基香豆素会同时通过 O-脱乙基反应氧化成 7-羟基香豆素,并通过 3-羟基反应氧化成 3-羟基、7-乙氧基香豆素。高活性突变体还能代谢其他几种人类 P450 底物,包括苯乙酮、乙氧基瑞舒芬和氯唑沙宗。这些结果表明,靛蓝的形成提供了一种简单的检测方法,可用于鉴定具有更大人类 P450 活性潜力的 CYP102A1 突变体。此外,我们的计算结果表明,结合位点的稳定性与 CYP102A1 突变体对香豆素的催化效率之间存在相关性:结合位点的结构越稳定,能量障碍越低,催化效率越高。