Discovery of a novel (R)-selective bacterial hydroxynitrile lyase from Acidobacterium capsulatum

Hydroxynitrile lyases (HNLs) are powerful carbon–carbon bond forming enzymes. The reverse of their natural reaction – the stereoselective addition of hydrogen cyanide (HCN) to carbonyls – yields chiral cyanohydrins, versatile building blocks for the pharmaceutical and chemical industry. Recently, bacterial HNLs have been discovered, which represent a completely new type: HNLs with a cupin fold. Due to various benefits of cupins (e.g. high yield recombinant expression in Escherichia coli), the class of cupin HNLs provides a new source for interesting, powerful hydroxynitrile lyases in the ongoing search for HNLs with improved activity, enantioselectivity, stability and substrate scope. In this study, database mining revealed a novel cupin HNL from Acidobacterium capsulatum ATCC 51196 (AcHNL), which was able to catalyse the (R)-selective synthesis of mandelonitrile with significantly better conversion (97%) and enantioselectivity (96.7%) than other cupin HNLs

Crystallization of the novel S-adenosyl-L-methionine-dependent C-methyltransferase CouO from Streptomyces rishiriensis and preliminary diffraction data analysis

Recombinant Q9F8T9 protein from Streptomyces rishiriensis (CouO), an S-adenosyl-L-methionine-dependent C-methyltransferase, has been successfully cloned, expressed and purified. CouO was crystallized from a single condition in the Morpheus crystallization screen. A vitrified crystal diffracted to 2.05 Å resolution and belonged to space group P2(1), with unit-cell parameters a = 33.02, b = 82.87, c = 76.77 Å, β = 96.93°

Crystallization of the novel S-adenosyl-L-methionine-dependent C-methyltransferase CouO from Streptomyces rishiriensis and preliminary diffraction data analysis

Recombinant Q9F8T9 protein from Streptomyces rishiriensis (CouO), an S-adenosyl-L-methionine-dependent C-methyltransferase, has been successfully cloned, expressed and purified. CouO was crystallized from a single condition in the Morpheus crystallization screen. A vitrified crystal diffracted to 2.05 Å resolution and belonged to space group P2(1), with unit-cell parameters a = 33.02, b = 82.87, c = 76.77 Å, β = 96.93°

Crystal Structure and Catalytic Mechanism of CouO, a Versatile C-Methyltransferase from Streptomyces rishiriensis.

Friedel-Crafts alkylation of aromatic systems is a classic reaction in organic chemistry, for which regiospecific mono-alkylation, however, is generally difficult to achieve. In nature, methyltransferases catalyze the addition of methyl groups to a wide range of biomolecules thereby modulating the physico-chemical properties of these compounds. Specifically, S-adenosyl-L-methionine dependent C-methyltransferases possess a high potential to serve as biocatalysts in environmentally benign organic syntheses. Here, we report on the high resolution crystal structure of CouO, a C-methyltransferase from Streptomyces rishiriensis involved in the biosynthesis of the antibiotic coumermycin A1. Through molecular docking calculations, site-directed mutagenesis and the comparison with homologous enzymes we identified His120 and Arg121 as key functional residues for the enzymatic activity of this group of C-methyltransferases. The elucidation of the atomic structure and the insight into the catalytic mechanism provide the basis for the (semi)-rational engineering of the enzyme in order to increase the substrate scope as well as to facilitate the acceptance of SAM-analogues as alternative cofactors

Proposed reaction mechanism.

<p>Reaction mechanism for the Friedel–Crafts alkylation catalyzed by SAM-dependent <i>C</i>-methyltransferases, CouO from <i>Streptomyces rishiriensis</i> and NovO from <i>Streptomyces spheroides</i>.</p