MTRR

The MTRR gene provides instructions for making an enzyme called methionine synthase reductase. This enzyme is required for the proper function of another enzyme called methionine synthase. Methionine synthase helps process amino acids, the building blocks of proteins. Specifically, it converts the amino acid homocysteine to another amino acid, methionine, which is used to make proteins and other important compounds. After a period of activity, methionine synthase becomes inactive. Methionine synthase reductase reactivates methionine synthase so it can continue to produce methionine.

homocystinuria - caused by mutations in the MTRR gene

At least 15 mutations in the MTRR gene have been identified in people with homocystinuria. Some of these mutations change single amino acids in methionine synthase reductase, which prevents the enzyme from functioning normally. Other mutations lead to an abnormally small, nonfunctional version of the enzyme. Without methionine synthase reductase, homocysteine cannot be converted to methionine. As a result, homocysteine builds up in the bloodstream and methionine is depleted. Some of the excess homocysteine is excreted in urine. Researchers have not determined how altered levels of homocysteine and methionine lead to the health problems associated with homocystinuria.

other disorders - increased risk from variations of the MTRR gene

A specific version (variant) of the MTRR gene may be associated with an increased risk of having a child with spina bifida (a birth defect that affects the spinal cord) or Down syndrome (a condition characterized by intellectual disability and associated health problems). The variant replaces the nucleotide adenine with the nucleotide guanine at position 66 of the MTRR gene (written as A66G). (Nucleotides are the building blocks of DNA.) Researchers have not determined why there may be a connection between the A66G variant of the MTRR gene and the risk of spina bifida or Down syndrome. Many factors, however, play a part in determining the risk of these complex disorders.