Stereochemistry and mechanism of hydrogen transfer between NADPH and methylenetetrahydrofolate in the reaction catalyzed by methylenetetrahydrofolate reductase from pig liver

Methylenetetrahydrofolate reductase from pig liver is a flavoprotein that catalyzes the reduction of N 5,10 -methylenetetrahydrofolate (CH 2 -H 4 folate) to N 5 -methyltetrahydrofolate (CH 3 -H 4 folate) using reducing equivalents supplied by NADPH. In these studies, the physiological cofactor for methylenetetrahydrofolate reductase, flavin adenine dinucleotide, has been replaced by 8-demethyl-8-hydroxy-5-deaza-5-carbaflavin adenine dinucleotide hydroquinone (8-OH-5-deazaFADH 2 )