Cytochrome P450 125A4, the Third Cholesterol C-26 Hydroxylase from Mycobacterium smegmatis.
Cytochrome P450 125A4, the Third Cholesterol C-26 Hydroxylase from Mycobacterium smegmatis.
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DOI：
10.1021/acs.biochem.5b01029
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发表时间：
2015-11-24
期刊：
影响因子：
2.9
通讯作者：
Ortiz de Montellano PR
中科院分区：
文献类型：
--
作者：
Frank DJ;Waddling CA;La M;Ortiz de Montellano PR
结核分枝杆菌（Mtb）和耻垢分枝杆菌（Msmeg）可以以胆固醇作为唯一碳源生长。在Mtb中，胆固醇的利用可由CYP 125 A1或CYP 142 A1启动，在Msmeg中，胆固醇的利用可由邻位酶CYP 125 A3和CYP 142 A2启动。Mtb中两种酶的双重敲除阻止了其在胆固醇上的生长，但Msmeg的双重敲除仍然能够生长，尽管速度较慢。我们在这里报告说，Msmeg有第三种酶，CYP 125 A4，也氧化胆固醇，虽然它对7α-羟基胆固醇的氧化活性要高得多。Msmeg CYP 125 A4（和Mtb CYP 125 A1）氧化7α-羟基胆固醇的能力至少部分是由于存在比CYP 125 A3更小的面向甾醇底物C-7的氨基酸侧链。氧化7-取代类固醇的能力拓宽了用于生长的甾醇碳源的范围，但更重要的是，在Mtb中，由于7α，26-二羟基胆固醇的强效免疫调节活性，可能产生额外的生物学效应。
Mycobacterium tuberculosis (Mtb) and Mycobacterium smegmatis (Msmeg) can grow on cholesterol as the sole carbon source. In Mtb the utilization of cholesterol can be initiated by CYP125A1 or CYP142A1 and in Msmeg by the orthologous CYP125A3 and CYP142A2. Double knockout of the two enzymes in Mtb prevents its growth on cholesterol, but the double knockout of Msmeg is still able to grow, albeit at a slower rate. We report here that Msmeg has a third enzyme, CYP125A4, that also oxidizes cholesterol, although it has a much higher activity for the oxidation of 7α-hydroxycholesterol. The ability of Msmeg CYP125A4 (and Mtb CYP125A1) to oxidize 7α-hydroxycholesterol is due, at least in part, to the presence of a smaller amino acid side chain facing C-7 of the sterol substrate than in CYP125A3. The ability to oxidize 7-substituted steroids broadens the range of sterol carbon sources for growth, but even more importantly in Mtb, additional biological effects are possible due to the potent immunomodulatory activity of 7α,26-dihydroxycholesterol.