Unexpected NADPH Hydratase Activity in the Nitrile Reductase QueF from Escherichia coli.

ABSTRACT: The nitrile reductase QueF catalyzes NADPH-dependent reduction of the nitrile group of preQ₀ (7-cyano-7-deazaguanine) into the primary amine of preQ₁ (7-aminomethyl-7-deazaguanine), a biologically unique reaction important in bacterial nucleoside biosynthesis. Here we have discovered that the QueF from Escherichia coli-its D197A and E89L variants in particular (apparent k_cat ≈10^-2  min^-1 )-also catalyze the slow hydration of the C5=C6 double bond of the dihydronicotinamide moiety of NADPH. The enzymatically C6-hydrated NADPH is a 3.5:1 mixture of R and S forms and rearranges spontaneously through anomeric epimerization (β→α) and cyclization at the tetrahydronicotinamide C6 and the ribosyl O2. NADH and 1-methyl- or 1-benzyl-1,4-dihydron

SUBMITTER: Jung J 

PROVIDER: S-EPMC7317782 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature