植物乳杆菌p-8转化亚油酸为共轭亚油酸的分析

研究植物乳杆菌（Lactobacillus plantarum）p-8的菌体、菌体破碎液和重组亚油酸异构酶系转化亚油酸（linoleic acid，LA）为共轭亚油酸（conjugated linoleic acid，CLA）的能力和机制。结果表明：L. plantarum p-8在含有LA的MRS上清液和菌体破碎液体外催化LA时，都可以低效产生cis9,trans11-CLA（c9,t11-CLA）、trans10,cis12-CLA（t10,c12-CLA）和trans9,trans11-CLA（t9,t11-CLA），但菌体中只有很少的t10,c12-CLA。实时聚合酶链式反应结果表明，亚油酸异构酶系的表达水平较低可能是CLA产量较低的原因。独立表达的重组亚油酸异构酶系成员、黄素腺嘌呤二核苷酸（flavin denine dinucleotide，FAD）和烟酰胺腺嘌呤二核苷酸都存在才可完成LA转化为c9,t11-CLA、t10,c12-CLA和t9,t11-CLA，转化途径与L. plantarum AUK1009一致。L. plantarum p-8的亚油酸水合酶经同源建模后有3 个结构域，底物结合位点与FAD位点位于3 个结构域连接处的疏水空腔中，M76和Y180是2 个必需基团。

Conversion of Linoleic Acid to Conjugated Linoleic Acid by Lactobacillus plantarum p-8

In this study, the ability of whole and disrupted cells of Lactobacillus plantarum p-8 and recombinant linoleate isomerase family from this strain to convert linoleic acid (LA) to conjugated linoleic acid (CLA) were evaluated and the underlying mechanism was explored. The results showed that whole and disrupted cells of L. plantarum p-8 cultured in MRS medium could inefficiently catalyze the conversion of LA to c9,t11-CLA, t10,c12-CLA and t9,t11-CLA, and only a small amount of t10,c12-CLA was observed in the cells. The results of real-time PCR exhibited that lower expression levels of linoleate isomerase family may be responsible for lower CLA production. Members of the independently expressed recombinant linoleate isomerase family, flavin denine dinucleotide (FAD) and nicotinamide adenine dinucleotide were found essential for the conversion of LA to c9,t11-CLA, t10,c12-CLA and t9,t11-CLA through a pathway consistent with that in L. plantarum AUK1009. Homologous modeling of linoleic acid hydrase presented three domains. The substrate-binding site and the FAD site were located in the hydrophobic cavity at the junction of the three domains. M76 and Y180 were essential residues.