What does Cystathionine beta-synthase do?
What does Cystathionine beta-synthase do?
Cystathionine beta-synthase (CBS) is the first enzyme in the transsulfuration pathway, catalyzing the conversion of serine and homocysteine to cystathionine and water.
Which of the following is a cofactor for Cystathionine B synthase?
pyridoxal-phosphate
CBS uses the cofactor pyridoxal-phosphate (PLP) and can be allosterically regulated by effectors such as the ubiquitous cofactor S-adenosyl-L-methionine (adoMet).
What is CBS enzyme?
The CBS gene provides instructions for making an enzyme called cystathionine beta-synthase. This enzyme acts in a chemical pathway and is responsible for using vitamin B6 to convert building block of proteins (amino acid) called homocysteine and serine to a molecule called cytathionine.
Where is the CBS gene located?
The catalytic domain of the CBS protein is located in the N-terminal 409 amino acids, and a regulatory domain is located in the C-terminal 142 amino acids.
What causes cysteine deficiency?
Cysteine deficiencies identified by inherited metabolic disorders or reduced levels in body fluid have been associated with: 1) impaired antioxidant defenses; 2) decreased ability to metabolize drugs or toxic compounds; 3) depressed immune functions; 4) some psycoses; and 5) homocystinemia.
What is CBS in physiology?
Cystathionine β-synthase (CBS) regulates homocysteine metabolism and contributes to hydrogen sulfide (H2S) biosynthesis through which it plays multifunctional roles in the regulation of cellular energetics, redox status, DNA methylation, and protein modification.
What type of reaction is involved in the first step of reaction to form Cystathionine?
beta-replacement reaction
Cystathionine beta-synthase (CBS) is a pyridoxal-phosphate-dependent enzyme that catalyzes a beta-replacement reaction in which the hydroxyl group of serine (L-Ser) is displaced by the thiol of homocysteine (L-Hcys) to form cystathionine (L-Cth) in the first step of the trans-sulfuration pathway.
What is CBS deficiency?
Abstract. Cystathionine beta-synthase (CBS) deficiency is a rare inherited disorder in the methionine catabolic pathway, in which the impaired synthesis of cystathionine leads to accumulation of homocysteine. Patients can present to many different specialists and diagnosis is often delayed.
What is CBS mutation?
This form of homocystinuria is caused by a genetic mutation in the CBS gene , which leads to low levels or absence of an enzyme called cystathionine beta-synthase (CBS). When CBS is absent or not working right, homocysteine and other toxic chemicals build up in the blood and urine.
How common is CBS gene mutation?
Approximately 1 in 200,000 to 1 in 300,000 people in the US has homocystinuria due to CBS deficiency. In other countries, the prevalence is higher.
What does homocysteine turn into?
In the body, homocysteine can be recycled into methionine or converted into cysteine with the aid of certain B-vitamins.
What is the structure of cystathionine β-synthase?
The human enzyme cystathionine β-synthase is a tetramer and comprises 551 amino acids with a subunit molecular weight of 61 kDa. It displays a modular organization of three modules with the N-terminal heme domain followed by a core that contains the PLP cofactor. The cofactor is deep in the heme domain and is linked by a Schiff base.
How do you convert homocysteine to cysteine?
Cysteine metabolism. Cystathionine beta synthase catalyzes the upper reaction and cystathionine gamma-lyase catalyzes the lower reaction. Transsulfuration, catalyzed by CBS, converts homocysteine to cystathionine, which cystathione gamma lyase converts to cysteine.
What is the EC number of Methylcysteine synthase?
Methylcysteine synthase was assigned the EC number EC 4.2.1.23 in 1961. A side-reaction of CBS caused this. The EC number EC 4.2.1.23 was deleted in 1972. Sequence and secondary structure of the CBS enzyme. The human enzyme cystathionine β-synthase is a tetramer and comprises 551 amino acids with a subunit molecular weight of 61 kDa.
What is the alternative metabolic pathway for cysteine synthesis?
One of the alternate reactions involving CBS is the condensation of cysteine with homocysteine to form cystathionine and hydrogen sulfide (H 2 S). H 2 S in the brain is produced from L-cysteine by CBS. This alternative metabolic pathway is also dependent on adoMet.
