Purification and kinetic mechanism of 5,10-metliyienetetrahydrofolate reductase from sheep liver

Identification of amino acid residues essential for enzyme activity of sheep liver 5,10-methylenetetrahydrofolate reductase

“…Enzyme preparation. Enzyme was purified and assayed as described previously (Varalakshmi et al, 1983). Protein was estimated by the method of Lowry et al (1951), with bovine serum albumin as standard.…”

“…The enzyme 5, 10-methylenetetrahydrofolate (5,10-CH2-H,folate) reductase (EC 1.1.99.5), which catalyses the nicotinamide nucleotide-dependent reduction of 5,10-CH2-H4folate to 5-methyltetrahydrofolate (5-CH3-H4folate), was isolated from sheep liver in a homogeneous form, and the kinetic mechanism of the reaction was established to be Bi Bi Ping Pong (Varalakshmi et al, 1983). A similar mechanism was earlier proposed for this enzyme from pig liver (Matthews, 1982).…”

Flavin-Dependent Enzymes in Cancer Prevention

“…5,10-Methylenetetrahydrofolate reductase (MTHFR ) is present in both prokaryotic and eukaryotic organisms [21–27] and the sequences of human methylenetetrahydrofolate reductase show clear homology with their bacterial analogs [28]. MTHFR catalyze the NAD(P)H-dependent reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate.…”

“…It was shown that the bacterial enzyme-bound flavin was reduced by NADH, and much more slowly by NADPH while the mammalian enzymes use NADPH [24,26,28]. Reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate creates tetrahydrofolate-bound one-carbon units used in the methylation of homocysteine to form methionine, the terminal step in methionine biosynthesis [21–26,28–30]. …”

“…5,10-Methylenetetrahydrofolate reductase is a multicomponent enzyme consisting of 2–4 subunits, each of them containing a molecule of non-covalently bound flavin adenine dinucleotide [21,24,26,28,29,31]. Human MTHFR gene has been localized at the end of the short arm of chromosome 1 (1p36.3).…”