(Methionine synthase) reductase
Template:Short description Template:Infobox enzyme [Methionine synthase] reductase, or Methionine synthase reductase,[1] encoded by the gene MTRR, is an enzyme that is responsible for the reduction of methionine synthase inside human body. This enzyme is crucial for maintaining the one carbon metabolism, specifically the folate cycle. The enzyme employs one coenzyme, flavoprotein.
Mechanism
MTRR works by catalyzing the following chemical reaction:
- 2 [methionine synthase]-methylcob(I)alamin + 2 S-adenosylhomocysteine + NADPTemplate:Sup 2 [methionine synthase]-cob(II)alamin + NADPH + HTemplate:Sup + 2 S-adenosyl-L-methionine
The 3 products of this enzyme are methionine synthase-methylcob(I)alamin, S-adenosylhomocysteine, and [[nicotinamide adenine dinucleotide phosphate|NADPTemplate:Sup]], whereas its 4 substrates are methionine synthase-cob(II)alamin, NADPH, [[hydrogen ion|HTemplate:Sup]], and S-adenosyl-L-methionine.
Physiologically speaking, one crucial enzyme in the folate cycle is methionine synthase, which incorporates the coenzyme cobalamin (also known as Vitamin B12). The coenzyme utilizes its cofactor, cobalt to catalyze the transferring function, in which the cobalt will switch between having 1 or 3 valence electrons, dubbed cob(I)alamin, and cob(III)alamin.
Over time, the cob(I)alamin cofactor of methionine synthase becomes oxidized to cob(II)alamin, rendering the enzyme inactive. Therefore, regeneration of the enzyme is necessary. Regeneration requires reductive methylation via a reaction catalyzed by (methionine synthase) reductase in which S-adenosylmethionine is utilized as a methyl donor, reducing cob(II)alamin to cob(I)alamin.[2]
Systematic naming
This enzyme belongs to the family of oxidoreductases, to be specific those oxidizing metal ion with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is [methionine synthase]-methylcob(I)alamin,S-adenosylhomocysteine:NADP+ oxidoreductase. Other names in common use include methionine synthase cob(II)alamin reductase (methylating), methionine synthase reductase, [methionine synthase]-cobalamin methyltransferase (cob(II)alamin, and reducing).
References
Template:Other oxidoreductases Template:Enzymes Template:Portal bar
- ↑ While including parentheses is the correct usage since this denotes the substrate being reduced, it is often omitted as omitting parentheses generally cause no confusion.
- ↑ Template:Cite journal