Cryogenic and laser photoexcitation studies identify multiple roles for active site residues in the light-driven enzyme protochlorophyllide oxidoreductase.

ABSTRACT: The light-activated enzyme NADPH-protochlorophyllide oxidoreductase (POR) catalyzes the trans addition of hydrogen across the C-17-C-18 double bond of protochlorophyllide (Pchlide), a key step in chlorophyll biosynthesis. Similar to other members of the short chain alcohol dehydrogenase/reductase family of enzymes, POR contains a conserved Tyr and Lys residue in the enzyme active site, which are implicated in a proposed reaction mechanism involving proton transfer from the Tyr hydoxyl group to Pchlide. We have analyzed a number of POR variant enzymes altered in these conserved residues using a combination of steady-state turnover, laser photoexcitation studies, and low temperature fluorescence spectroscopy. None of the mutations completely abolished catalytic activity. We demonstrate their

SUBMITTER: Menon BR 

PROVIDER: S-EPMC2709359 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature