CBS Gene Mutation – (Cystathionine -Synthase Gene Mutation)

The cystathionine beta synthase (CBS) enzyme converts homocysteine

to cystathionine. The two most common mutations in the CBS gene are

the G919A and T833C substitutions resulting in a serine for glycine at

amino acid residue 307 and a threonine for isoleucine at amino acid 278,


Patients with the T833C mutation can respond to pyridoxine therapy,

whereas, patients with the G919A mutation do not respond to pyridoxine

therapy. Thus, identification of these CBS mutations would help in the

diagnosis and treatment of homocysteinemia.


1. Sperandeo, M.P., M. Panico, A. Pepe, et al., (1995) Molecular analysis

of patients affected by homocysteinuria due to cystathionine b-synthase

deficiency: report of a new mutation in exon 8 and a deletion in intron 11.

J. Inher. Metab. Dis. 18:211-4.

2. Hu, F.L., Z. Gu, V. Kozich, et al, Molecular basis of cystathionine

b-synthase deficiency in pyridoxine responsive and nonresponsive

homocystinuria. Hum Molec. Gen. 2:1857-60.

3. Sperandeo, M.P., M. Candito, G. Sebastio, et al., (1996) Homocysteine

response to methionine chalenge in four obligate heterozygotes for

homocysteinuria and relationship with cystathionine b-synthase

mutations. J. Inher. Metab. Dis. 19:351-6.

4. Kraus, J.P. (1994) Molecular basis of phenotype expression in

homocystinuria. J. Inher. Metab. Dis. 17:383-90.

5. Glueck, C. J., R. N. Fontaine, A. Gupta and M. Alasmi (1997)

Myocardial infarction in a 35-year-old man with homocysteinemia, high

plasminogen activator inhibitor activity, and resistance to activated

protein C. Metabolism 46:1470-2.

6. Glueck, C.J. M.J. Kupferminc, R.N. Fontaine, P. Wang, B.B. Weksler

and A. Eldor. (2001) Genetic hypofibrinolysis in complicated

pregnancies. Obstet. and Gynecol. 97:44-8.

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