   1.17.1.3 | (2R,3S)-catechin + NADP+ + H2O = 2,3-trans-3,4-cis-leucocyanidin + NADPH + H+ |
two-step catalytic mechanism involving the formation of an enzyme-bound quinone methide intermediate prior to reduction, overview. A concerted dehydration precedes an NADPH-mediated hydride transfer at C4. The dehydration step involves a Lys-catalyzed deprotonation of the phenolic OH7 through a bridging water molecule and a His-catalyzed protonation of the benzylic hydroxyl at C4. The resulting quinone methide serves as an electrophilic target for hydride transfer at C4. The role of the lysine is to promote the formation of this intermediate by catalyzing the deprotonation of a phenolic hydroxyl |
715907 |
