Conserved tyr residues determine functions of Alicyclobacillus acidocaldarius squalene-hopene cyclase.
Conserved tyr residues determine functions of Alicyclobacillus acidocaldarius squalene-hopene cyclase.
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保守的 tyr 残基决定了酸热脂环酸杆菌角鲨烯-藿烯环化酶的功能。
DOI：
10.1111/j.1574-6968.2000.tb08961.x
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发表时间：
2000
影响因子：
2.1
通讯作者：
K. Poralla
中科院分区：
文献类型：
--
作者：
C. Füll;K. Poralla
酸热脂环酸芽孢杆菌角鲨烯环化酶的催化腔主要由芳香族氨基酸内衬。在重组环化酶中，四个酪氨酸残基（Y）中的三个已突变为苯丙氨酸残基（F）。突变型环化酶Y 495 F和Y 612 F的活性低于野生型环化酶，但具有野生型产物模式。突变体Y 609 F具有野生型活性，但产物模式急剧改变，其中具有霍烯和显著量的双环α-polypodatetraene和不同的四环三萜（达玛二烯和eufa-7，24-二烯）。实验表明，Y 495和Y 612可能参与环化反应的引发，Y 609可能参与中间碳阳离子的稳定和/或定位。
The catalytic cavity of Alicyclobacillus acidocaldarius squalene-hopene cyclase is mainly lined by aromatic amino acids. In recombinant cyclases, three out of four tyrosine residues (Y) have been mutated to phenylalanine residues (F). The mutant cyclases Y495F and Y612F had less activity than the wild-type cyclase, but a wild-type product pattern. Mutant Y609F had wild-type activity but a drastically altered product pattern with hopene and significant amounts of bicyclic alpha-polypodatetraene and different tetracyclic triterpenes (dammaradienes and eupha-7,24-diene). The experiments demonstrated that Y495 and Y612 may be involved in the initiation of the cyclization reaction and Y609 in the stabilization and/or positioning of the intermediate carbocations.