Classic homocystinuria is caused by deficiency of cystathionine β-synthase (CBS), a pyridoxine (vitamin B6)-dependent enzyme.
Cystathionine β-synthase is an enzyme that breaks down methionine. Cystathionine β-synthase is an enzymes that converts homocysteine to cystathionine in the trans-sulphuration pathway of the methionine cycle and requires pyridoxal 5-phiosphate as a cofactor. The other two cofactors involved in demethylation pathway of methionine include vitamin B12 and folic acid.A deficiency of this enzyme leads to a build-up of toxic homocysteine in the body.
Classic homocystinuria consists of chronic intoxication, without acute decompensation except for vascular accidents and acute psychiatric episodes, where the diversity of clinical manifestations makes diagnosis difficult and often delays it until late childhood or adulthood.
Homocystinuria and vitamin B6
