手性化合物/药物的生物酶合成

李兆良 2019.7.1

早已放下实验室工作多年。看到冯大诚老师的博客谈手性化合物，想起30多年前的工作，看来现在慢慢被重视。我分离的酶与植物次代谢途径现在已经很多人在接着做。

用生物酶合成药用化合物作为药物是我的在普渡大学博士论文——麦角碱的前体Dimethylallyl tryptophan合成的第一个酶的提纯 （1975），首次发现植物次生代谢物也有生成反馈抑制，证明并非植物产生的废料。Dimethylallyl tryptophan 本身没有手性，它的衍生物才有。我耶鲁博士后的研究Biosynthesis of ajmalicine (1976) 是承接这主题，真正产生手性化合物的研究。生成长春花碱（治癌药）的植物Periwinkle，也产生Ajmalicine。Ajamlicine的生物合成是酶合成手性化合物的第一例子。

这是一段美好的回忆。是我人生中五段专业之一：实验科学，科学管理，互联网商业，书法，历史研究。民族音乐只算是业余爱好，没有经济收入，就不算专业了。

下面是主要的论文：

Isolation of dimethylallylpyrophosphate: Tryptophan dimethylallyl transferase from the ergot fungus (Claviceps spec.) P F Heinstein, S I Lee, H G Floss  Biochemical and Biophysical Research Communications 44(5):1244-51 · October 1971

https://www.sciencedirect.com/science/article/abs/pii/0003986176904185  Purification and properties of dimethylallylpyrophosphate: Tryptophan dimethylallyl transferase, the first enzyme of ergot alkaloid biosynthesis in Claviceps. sp. SD 58. Siu-Leung Lee, P.F.Heinstein, H.G. Floss.  Archives of Biochemistry and Biophysics Volume 177, Issue 1,  November 1976, Pages 84-94。

Dimethylallylpyrophosphate:l-tryptophan dimethylallyltransferase (DMAT synthetase), the first pathway-specific enzyme of ergot alkaloid biosynthesis, has been isolated from mycelia of Claviceps sp., strain SD 58, and purified to apparent homogeneity. The enzyme reaction products were identified as l-4-(γ,γ-dimethylallyl)tryptophan and inorganic pyrophosphate. DMAT synthetase is a single subunit protein of molecular weight 70,000–73,000 and has an isoelectric point at pH 5.8. The enzyme is activated by Fe2+, Mg2+, and particularly Ca2+; Kmvalues for l-tryptophan and dimethylallylpyrophosphate were determined to be 0.067 and 0.2 mm, respectively. Kinetic analysis indicated that the DMAT synthetase reaction proceeds by a sequential rather than a ping-pong mechanism.

https://www.researchgate.net/publication/256128941_Indole_alkaloid_biosynthesis_Partial_purification_of_ajmalicine_synthetase_from callus, seedlings and mature plants. 

李兆良 2019.7.1