ID 2.1.1.13 DE methionine synthase. AN 5-methyltetrahydrofolate--homocysteine S-methyltransferase. AN 5-methyltetrahydrofolate--homocysteine transmethylase. AN B12 N(5)-methyltetrahydrofolate homocysteine methyltransferase. AN cobalamin-dependent methionine synthase. AN methionine synthase (cobalamin-dependent). AN methionine synthetase. AN methyltetrahydrofolate--homocysteine vitamin B12 methyltransferase. AN N(5)-methyltetrahydrofolate--homocysteine cobalamin methyltransferase. AN N(5)-methyltetrahydrofolate methyltransferase. AN N(5)-methyltetrahydrofolic--homocysteine vitamin B12 transmethylase. AN N-methyltetrahydrofolate:L-homocysteine methyltransferase. AN tetrahydrofolate methyltransferase. AN tetrahydropteroylglutamate methyltransferase. AN tetrahydropteroylglutamic methyltransferase. AN vitamin B12 methyltransferase. CA (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8- CA tetrahydrofolate + L-methionine. CC -!- The enzyme becomes inactivated occasionally during its cycle by CC oxidation of Co(I) to Co(II). CC -!- Reactivation by reductive methylation is catalyzed by the enzyme CC itself, with S-adenosyl-L-methionine as the methyl donor and a CC reducing system. CC -!- For the mammalian enzyme, the reducing system involves NADPH and CC EC 1.16.1.8. CC -!- In bacteria, the reducing agent is flavodoxin, and no further CC catalyst is needed (the flavodoxin is kept in the reduced state by CC NADPH and EC 1.18.1.2). CC -!- Acts on the monoglutamate as well as the triglutamate folate, CC in contrast with EC 2.1.1.14, which acts only on the triglutamate. DR Q5E814, METH_ALIF1 ; Q9AJQ8, METH_ALIFS ; Q4JIJ3, METH_BOVIN ; DR A8XY95, METH_CAEBR ; Q09582, METH_CAEEL ; Q54P92, METH_DICDI ; DR P13009, METH_ECOLI ; Q99707, METH_HUMAN ; A6H5Y3, METH_MOUSE ; DR Q49775, METH_MYCLE ; O33259, METH_MYCTU ; Q9I2Q2, METH_PSEAE ; DR O33465, METH_PSEPU ; Q9Z2Q4, METH_RAT ; P37586, METH_SALTY ; DR Q55786, METH_SYNY3 ; Q9KUW9, METH_VIBCH ; Q87L95, METH_VIBPA ; DR Q8DCJ7, METH_VIBVU ; Q7MHB1, METH_VIBVY ; //