Cystathionine Beta Synthase - Human Disease

Human Disease

Down syndrome is a medical condition characterized by an overexpression of cystathionine beta synthase (CBS) and a low level of homocysteine in the blood. It has been speculated that cystathionine beta synthase overexpression could be the major culprit in this disease (along with dysfunctioning of GabaA and Dyrk1a). The phenotype of down syndrome is the opposite of Hyperhomocysteinemia (described below). Pharmacologicals inhibitors of CBS have been patented by the Jerome Lejeune Foundation (November 2011) and trials (animals and humans are planned).

Hyperhomocysteinemia is a medical condition characterized by an abnormally large level of homocysteine in the blood. Mutations in CBS are the single most common cause of hereditary hyperhomocysteinemia. Inborn errors in CBS result in hyperhomocysteinemia with complications in the cardiovascular system leading to early and aggressive arterial disease. Hyperhomocysteinemia also affects three other major organ systems including the ocular, central nervous, and skeletal.

Homocystinuria due to CBS deficiency is a special type of hyperhomocysteinemia. It is a rare, hereditary recessive autosomal disease, in general, diagnosed during childhood. A total of 131 different homocystinuria-causing mutations have been identified. A common functional feature of the mutations in the CBS domains is that the mutations abolish or strongly reduce activation by adoMet. No specific cure has been discovered for homocystinuria; however, many people are treated using high doses of vitamin B₆, which is a cofactor of CBS.