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首页> 外文期刊>Applied and Environmental Microbiology >Genetic and Biochemical Characterization of a Novel Monoterpene ?-Lactone Hydrolase from Rhodococcus erythropolis DCL14
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Genetic and Biochemical Characterization of a Novel Monoterpene ?-Lactone Hydrolase from Rhodococcus erythropolis DCL14

机译：赤红球菌DCL14的新型单萜β-内酯水解酶的遗传和生化特性。

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A monoterpene ?-lactone hydrolase (MLH) from Rhodococcus erythropolis DCL14, catalyzing the ring opening of lactones which are formed during degradation of several monocyclic monoterpenes, including carvone and menthol, was purified to apparent homogeneity. It is a monomeric enzyme of 31 kDa that is active with (4R)-4-isopropenyl-7-methyl-2-oxo-oxepanone and (6R)-6-isopropenyl-3-methyl-2-oxo-oxepanone, lactones derived from (4R)-dihydrocarvone, and 7-isopropyl-4-methyl-2-oxo-oxepanone, the lactone derived from menthone. Both enantiomers of 4-, 5-, 6-, and 7-methyl-2-oxo-oxepanone were converted at equal rates, suggesting that the enzyme is not stereoselective. Maximal enzyme activity was measured at pH 9.5 and 30°C. Determination of the N-terminal amino acid sequence of purified MLH enabled cloning of the corresponding gene by a combination of PCR and colony screening. The gene, designated mlhB(monoterpene lactone hydrolysis), showed up to 43% similarity to members of the GDXG family of lipolytic enzymes. Sequencing of the adjacent regions revealed two other open reading frames, one encoding a protein with similarity to the short-chain dehydrogenase reductase family and the second encoding a protein with similarity to acyl coenzyme A dehydrogenases. Both enzymes are possibly also involved in the monoterpene degradation pathways of this microorganism.
机译：来自红红球菌DCL14的单萜β-内酯水解酶（MLH）被催化至内在均质，该内酯催化在内酯的开环反应，所述内酯在包括香芹酮和薄荷醇的几种单环单萜降解期间形成。它是一种31 kDa的单体酶，与（4R）-4-异丙烯基-7-甲基-2-氧代-氧杂戊酮和（6R）-6-异丙烯基-3-甲基-2-氧代-氧杂戊酮具有活性，是由内酯衍生的由（4R）-二氢香芹酮和7-异丙基-4-甲基-2-氧代-氧杂戊酮（由薄荷酮衍生的内酯）制成。 4-，5-，6-和-7-甲基-2-氧代-氧杂戊酮的对映体均以相同的速率转化，表明该酶不是立体选择性的。在pH 9.5和30°C下测量最大酶活性。纯化的MLH的N末端氨基酸序列的确定使得能够通过PCR和菌落筛选的组合来克隆相应的基因。该基因命名为mlhB（单萜内酯水解），与脂解酶GDXG家族成员的同源性高达43％。相邻区域的测序揭示了另外两个开放阅读框，一个阅读框编码与短链脱氢酶还原酶家族相似的蛋白质，第二个阅读框编码与酰基辅酶A脱氢酶相似的蛋白质。两种酶都可能也参与了该微生物的单萜降解途径。

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