Kinetic and molecular analysis of 5-epiaristolochene 1,3-dihydroxylase, a cytochrome P450 enzyme catalyzing successive hydroxylations of sesquiterpenes.

ABSTRACT: The final step of capsidiol biosynthesis is catalyzed by 5-epiaristolochene dihydroxylase (EAH), a cytochrome P450 enzyme that catalyzes the regio- and stereospecific insertion of two hydroxyl moieties into the bicyclic sesquiterpene 5-epiaristolochene (EA). Detailed kinetic studies using EA and the two possible monohydroxylated intermediates demonstrated the release of 1beta-hydroxy-EA ((OH)EA) at high EA concentrations and a 10-fold catalytic preference for 1beta(OH)EA versus 3alpha(OH)EA, indicative of a preferred reaction order of hydroxylation at C-1, followed by that at C-3. Sequence alignments and homology modeling identified active-site residues tested for their contribution to substrate specificity and overall enzymatic activity. Mutants EAH-S368C and EAH-S368V exhibited wild-type

SUBMITTER: Takahashi S 

PROVIDER: S-EPMC2859954 | biostudies-literature | 2005 Feb

REPOSITORIES: biostudies-literature