Nagata Y, Miyauchi K, Takagi M
Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
J Ind Microbiol Biotechnol. 1999 Oct;23(4-5):380-390. doi: 10.1038/sj.jim.2900736.
gamma-Hexachlorocyclohexane (gamma-HCH; also called BHC or lindane) is one of the highly chlorinated pesticides which can cause serious environmental problems. Sphingomonas paucimobilis UT26 degrades gamma-HCH under aerobic conditions. The unique degradation pathway of gamma-HCH in UT26 is revealed. In the upstream pathway, gamma-HCH is transformed to 2,5-dichlorohydroquinone (2,5-DCHQ) by two different dehalogenases (LinA and LinB) and one dehydrogenase (LinC) which are expressed constitutively. In the downstream pathway, 2,5-DCHQ is reductively dehalogenated, and then ring-cleaved by enzymes (LinD and LinE, respectively) whose expressions are regulated. We have cloned and sequenced five structural genes (linA, linB, linC, linD, and linE) directly involved in this degradation pathway. The linD and linE genes form an operon, and its expression is positively regulated by the LysR-type transcriptional regulator (LinR). The genes linA, linB, and linC are constitutively expressed, and are present separately from each other in the UT26 genome. Cell fractionation analysis, Western blotting, and immuno electron microscopy revealed that LinA and LinB are localized in the periplasmic space of UT26.
γ-六氯环己烷（γ-HCH；也称为六六六或林丹）是一种高氯化农药，会导致严重的环境问题。少动鞘氨醇单胞菌UT26在有氧条件下降解γ-HCH。揭示了UT26中γ-HCH独特的降解途径。在上游途径中，γ-HCH通过两种组成型表达的不同脱卤酶（LinA和LinB）和一种脱氢酶（LinC）转化为2,5-二氯对苯二酚（2,5-DCHQ）。在下游途径中，2,5-DCHQ被还原脱卤，然后分别由表达受调控的酶（分别为LinD和LinE）进行开环。我们已经克隆并测序了直接参与该降解途径的五个结构基因（linA、linB、linC、linD和linE）。linD和linE基因形成一个操纵子，其表达受LysR型转录调节因子（LinR）的正调控。linA、linB和linC基因组成型表达，在UT26基因组中彼此分开存在。细胞分级分离分析、蛋白质印迹和免疫电子显微镜显示，LinA和LinB定位于UT26的周质空间。
