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Pathway Description
Homocystinuria-Megaloblastic Anemia Due to Defect in Cobalamin Metabolism, cblG Complementation Type
Homo sapiens
Disease Pathway
Homocystinuria-megaloblastic anemia due to defect in cobalamin metabolism, cblG complementation type, also known as methionine synthase deficiency or methylcobalamin deficiency, cblG type, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder of the methionine metabolim pathway. It is caused by a mutation in the MTR gene which encodes the enzyme methionine synthase. This enzyme is responsible for forming L-methionine and tetrahydrofolic acid from homocysteine and 5-methyltetrahydrofolic acid. When the enzyme is mutated, this leads to lower amounts of L-methionine in the cell, as well as increased levels of homocysteine. Methionine synthase deficiency is characterized by an increase in homocysteine levels in the body and excreted in the urine, as well as decreased levels of methionine in the blood. Symptoms include megaloblastic anemia, and can also include developmental delays, seisures and kidney failure. Treatment with vitamin B12, as well as folates and betaine is effective. It is estimated that methionine synthase deficiency affects less than 1 in 1,000,000 individuals.
References
Homocystinuria-Megaloblastic Anemia Due to Defect in Cobalamin Metabolism, cblG Complementation Type References
[Metagen: HOMOCYSTINURIA-MEGALOBLASTIC ANEMIA DUE TO DEFECT IN COBALAMIN METABOLISM, cblG COMPLEMENTATION TYPE](http://metagene.de/program/d.prg?id_d=532)
[OMIM: 250940](http://omim.org/entry/250940})
Watkins D, Rosenblatt DS: Functional methionine synthase deficiency (cblE and cblG): clinical and biochemical heterogeneity. Am J Med Genet. 1989 Nov;34(3):427-34. doi: 10.1002/ajmg.1320340320.
Pubmed: 2688421
Methionine Metabolism References
Lehninger, A.L. Lehninger principles of biochemistry (4th ed.) (2005). New York: W.H Freeman.
Salway, J.G. Metabolism at a glance (3rd ed.) (2004). Alden, Mass.: Blackwell Pub.
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