Preliminary assessment of the C13-side chain 2'-hydroxylase involved in taxol biosynthesis.
Preliminary assessment of the C13-side chain 2'-hydroxylase involved in taxol biosynthesis.
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初步评估参与紫杉醇生物合成的 C13 侧链 2-羟化酶。
DOI：
10.1016/j.bbrc.2005.08.119
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Croteau,Rodney
中科院分区：
文献类型：
--
作者：
Long,RobertM;Croteau,Rodney
紫杉（Taxus）物种中抗癌药物紫杉醇的生物合成被认为涉及高级紫杉烷二萜类中间体浆果赤霉素III的初步形成，随后在其上在C13-O-位置组装功能重要的N-苯甲酰基苯基异丝氨酰基侧链。用红豆杉组织进行的体内饲养研究和负责C13侧链构建的两种转移酶的表征表明了一个顺序过程，其中氨基变位酶将α-苯丙氨酸转化为β-苯丙氨酸，然后将其活化为相应的CoA酯并转移至浆果赤霉素III以产生β-苯丙氨酰基浆果赤霉素III（即，N-脱苯甲酰基-2 ′-脱氧紫杉醇），随后进行2′-羟基化和N-苯甲酰化，得到紫杉醇。然而，由于侧链转移酶可以在巴卡亭III的C13-O-酯化中利用β-苯丙氨酰CoA和苯基异丝氨酰CoA，因此关于2′-羟基化步骤是发生在氨基苯丙酰基部分转移之前还是之后仍然不明确。使用来自红豆杉悬浮细胞的无细胞酶系统，没有发现β-苯丙氨酸直接羟基化为苯基异丝氨酸的证据;然而，来自该组织的微粒体制剂似乎能够细胞色素P450介导的β-苯丙氨酰基浆果赤霉素III羟基化为苯基异丝氨酰基浆果赤霉素III（即，N-脱苯甲酰基紫杉醇）作为紫杉醇和相关N-取代紫杉烷形成的倒数第二步。这些初步结果，这是与建议的侧链组装过程，阐明了紫杉醇生物合成的一个重要步骤，并为克隆负责细胞色素P450羟化酶基因的基础。
The biosynthesis of the anticancer drug Taxol in yew (Taxus) species is thought to involve the preliminary formation of the advanced taxane diterpenoid intermediate baccatin III upon which the functionally important N-benzoyl phenylisoserinoyl side chain is subsequently assembled at the C13-O-position. In vivo feeding studies with Taxus tissues and characterization of the two transferases responsible for C13-side chain construction have suggested a sequential process in which an aminomutase converts α-phenylalanine to β-phenylalanine which is then activated to the corresponding CoA ester and transferred to baccatin III to yield β-phenylalanoyl baccatin III (i.e., N-debenzoyl-2′-deoxytaxol) that undergoes subsequent 2′-hydroxylation and N-benzoylation to afford Taxol. However, because the side chain transferase can utilize both β-phenylalanoyl CoA and phenylisoserinoyl CoA in the C13-O-esterification of baccatin III, ambiguity remained as to whether the 2′-hydroxylation step occurs before or after transfer of the amino phenylpropanoyl moiety. Using cell-free enzyme systems from Taxus suspension cells, no evidence was found for the direct hydroxylation of β-phenylalanine to phenylisoserine; however, microsomal preparations from this tissue appeared capable of the cytochrome P450-mediated hydroxylation of β-phenylalanoyl baccatin III to phenylisoserinoyl baccatin III (i.e., N-debenzoyltaxol) as the penultimate step in the formation of Taxol and related N-substituted taxoids. These preliminary results, which are consistent with the proposed side chain assembly process, have clarified an important step of Taxol biosynthesis and set the foundation for cloning the responsible cytochrome P450 hydroxylase gene.