Mechanistic aspects of cyanogenesis from active-site mutant Ser80Ala of hydroxynitrile lyase from Manihot esculenta in complex with acetone cyanohydrin.

ABSTRACT: The structure and function of hydroxynitrile lyase from Manihot esculenta (MeHNL) have been analyzed by X-ray crystallography and site-directed mutagenesis. The crystal structure of the MeHNL-S80A mutant enzyme has been refined to an R-factor of 18.0% against diffraction data to 2.1-A resolution. The three-dimensional structure of the MeHNL-S80A-acetone cyanohydrin complex was determined at 2.2-A resolution and refined to an R-factor of 18.7%. Thr11 and Cys81 involved in substrate binding have been substituted by Ala in site-directed mutagenesis. The kinetic measurements of these mutant enzymes are presented. Combined with structural data, the results support a mechanism for cyanogenesis in which His236 as a general base abstracts a proton from Ser80, thereby allowing proton transfer from

SUBMITTER: Lauble H 

PROVIDER: S-EPMC2374195 | biostudies-literature | 2001 May

REPOSITORIES: biostudies-literature