Center for Bioinformatics
Oxidoreductases | Transferases | Hydrolases | Lyases | Isomerases | Ligases

Basic Information

Enzyme Number

Official Name

cystathionine beta-synthase

Name from literature


Pathway from literature

the transsulfuration pathway

Pathway from KEGG

Amino Acid Metabolism; Glycine, serine and threonine metabolism; map00260

Metabolism of Other Amino Acids; Selenoamino acid metabolism; map00450

Amino Acid Metabolism; Methionine metabolism; map00271

Human Diseases; Neurodegenerative Diseases; Huntington's disease; map05040


Human (9606)

Genome localization

21q22.3[875 ],


A pyridoxal-phosphate protein. A multifunctional enzyme: catalyses beta-replacement reactions between L-serine, L-cysteine, cysteine thioethers, or some other beta-substituted alpha-L-amino acids, and a variety of mercaptans.

Rate-limiting Description

"We examined the presence of the gene for cystathionine-beta-synthase (CBS), the rate limiting enzyme that converts homocysteine to cystathionine in the transsulfuration pathway, in human lens epithelial (HLE) B3 cells using PCR with primers designed based on the sequence of human liver CBS (Forward 5'-CCA CAC TGC CCC GGC AAA AT-3'; Reverse 5'-CTG GCA ATG CCC GTG ATG GT-3')." (15642325)

Regulatory Information

Upstream transcription factor


Regulatory type


transcriptional factor;Sp1(6667)

"Sp1 has a critical and indispensable role in tissue-specific regulation of cystathionine beta-synthase" (14670973)

Gene ontology

Gene ontology

GO:0004122 (F) cystathionine beta-synthase activity [P35520 ];
GO:0030170 (F) pyridoxal phosphate binding [P35520 ];
GO:0019343 (P) cysteine biosynthetic process via cystathio... [P35520 ];
GO:0006535 (P) cysteine biosynthetic process from serine [P35520 ];
GO:0005829 (C) cytosol [P35520 ];
GO:0005506 (F) iron ion binding [P35520 ];
GO:0005730 (C) nucleolus [P35520 ];

Tissue expression

Tissue From HPRD

Lung [01994 ];
Heart [01994 ];
Skin [01994 ];
Pancreas [01994 ];
Liver [01994 ];
Brain [01994 ];

Tissue specificity

In the adult strongly expressed in liver and pancreas, some expression in heart and brain, weak expression in lung and kidney. In the fetus, expressed in brain, liver and kidney [P35520 ];

Subcellular localization


nucleus [P35520 ];

cytoplasm [P35520 ];

Disease relevance


Defects in CBS are the cause of cystathionine beta-synthase deficiency (CBSD) [MIM:236200]. It is a recessively inherited error of sulfur amino acid metabolism leading to homocystinuria. Homocystinuria is associated with elevated levels of homocysteine in the blood (homocysteinemia) [MIM:603174]. Patients with homocystinuria have also methionine in their body fluid and usually benefit from dietary and pharmacological treatment (high doses of pyridoxine and vitamin B6). Other characteristics are dislocated optic lenses, vascular disorders (arteriosclerosis and thrombosis), skeletal abnormalities, and mental retardation [P35520 ];




Entrez Gene




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  Last Modified: 2009-03-24  
  Design by Zhao Min