Strictosidine synthase: mechanism of a Pictet-Spengler catalyzing enzyme.

ABSTRACT: The Pictet-Spengler reaction, which yields either a beta-carboline or a tetrahydroquinoline product from an aromatic amine and an aldehyde, is widely utilized in plant alkaloid biosynthesis. Here we deconvolute the role that the biosynthetic enzyme strictosidine synthase plays in catalyzing the stereoselective synthesis of a beta-carboline product. Notably, the rate-controlling step of the enzyme mechanism, as identified by the appearance of a primary kinetic isotope effect (KIE), is the rearomatization of a positively charged intermediate. The KIE of a nonenzymatic Pictet-Spengler reaction indicates that rearomatization is also rate-controlling in solution, suggesting that the enzyme does not significantly change the mechanism of the reaction. Additionally, the pH dependence of the soluti

SUBMITTER: Maresh JJ 

PROVIDER: S-EPMC3079323 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature