Relationship Between Asymmetric Reduction Catalytic Ability Of Rhodobacter Sphaeroides And Substrate Structure

More and more people pay attention to asymmetric synthesis catalyzed by biological methods,especially in the drug intermediates synthesis area.At present,the asymmetric reduction of model substrate catalyzed by yeast,algae,plant cell or fungl microorganisms was studied. Based on the results of asymmetric reduction of model substrate by biocatalyst,conditions of biological catalysis have been elucidated that includ pH value, temperature, reaction time and substrate concentration and so on.The relationship between catalytic ability of the biocatalyst and the structure of substrate was a little studied.The results were different when different substrates were catalyzed by biocatalyst,so we will study that the relationship between catalytic ability of the biocatalyst and the structures of substrates.Herein we propose new biocatalyst that photosynthetic bacteria have the capacity of capturing light energy to generate NADPH through photosynthetic electron-transfer reactions and no oxygen were brought,which was able to catalyze potential ketone produce chiral alcohols by using luminous energy.The reaction mechanism is nuclear reactors,NADPH participates in the reaction process.Based on the mechanism,the relationship between catalytic ability of the Rhodobacter sphaeroides and the structures of substrates was further studied by evaluating the yields, ee value, activity of enzyme, and Km value, whose were obtained from the experiment.The result showed as follows:1.22 compounds were asymmetric hydrogenated by chemical reductant,the reduction of products were racemic mixture.Firstly,using automatic optical indicator detected optical activity of products;Secondly,establishing GC method and determining retention time of reduction of products.2. In the best conditions of reaction,22 substrates were asymmetric hydrogenated by whole cell of the Rhodobacter sphaeroides.The results showed that the ee value was followed by the Prelg rules. The yields were related to the substitution in benzene ring and side-chain of the actophenone. The yield reduced with the increasing of the length of the chain and molecular meight, but enhanced with the increasing of the number of branched-chains for aliphatic ketones.3. The co-enzyme regeneration system coupled with carbonyl reductase system was built through preparation of BCH1a and isolation and purification of carbonyl reductase of the Rhodobacter sphaeroides.4. Based on the study of the asymmetric reduction of latent chiral ketones by carbonyl reductase, it was found that there is a high specificities for pentanones in aliphatic ketones, as well as for the acetophenone derivates which contained a withdrawing group atα-position. With the usage of enzyme-catalyze in the asymmetric hydrogenation reaction, all the ee values were around 99%. The results also indicated that the carbonyl reductase has higher stereoselectivity than the whole-cell.