Interactions with the substrate phenolic group are essential for hydroxylation by the oxygenase component of p-hydroxyphenylacetate 3-hydroxylase.

ABSTRACT: p-Hydroxyphenylacetate (HPA) 3-hydroxylase is a two-component flavoprotein monooxygenase that catalyzes the hydroxylation of p-hydroxyphenylacetate to form 3,4-dihydroxyphenylacetate. Based on structures of the oxygenase component (C(2)), both His-120 and Ser-146 are located ~2.8 Å from the hydroxyl group of HPA. The variants H120N, H120Q, H120Y, H120D, and H120E can form C4a-hydroperoxy-FMN (a reactive intermediate necessary for hydroxylation) but cannot hydroxylate HPA. The impairment of H120N is not due to substrate binding because the variant can still bind HPA. In contrast, the H120K variant catalyzes hydroxylation with efficiency comparable with that of the wild-type enzyme; the hydroxylation rate constant for H120K is 5.7 ± 0.6 s(-1), and the product conversion ratio is 75%, compare

SUBMITTER: Tongsook C 

PROVIDER: S-EPMC3248019 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature