What is the function of cystathionine?

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 converts homocysteine to cystathionine?

Cystathionine beta-synthase
Cystathionine beta-synthase, along with vitamin B6, converts homocysteine to cystathionine (see Fig. 5-8). A deficiency of this enzyme leads to accumulation not only of homocysteine but also its precursor, methionine.

What type of reaction is involved in the first step of reaction to form Cystathionine?

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 the role of cystathionine beta-synthase?

The cystathionine ß-synthase (CBS) is a critical enzyme in the transsulfuration pathway and is responsible for the synthesis of cystathionine from serine and homocysteine. Cystathionine is a precursor to amino acid cysteine. CBS is also responsible for generation of hydrogen sulfide (H2S) from cysteine.

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 the role of Cystathionine beta-synthase?

Why is homocysteine test done?

A homocysteine test may be used to: Find out if you have deficiency in vitamin B12, B6, or folic acid. Help diagnose homocystinuria, a rare, inherited disorder that prevents the body from breaking down certain proteins. It can cause serious health problems and usually starts in early childhood.

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.

What is the 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.

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. The enzyme contains three functional domains.

What is cystathionine β-synthase?

Cystathionine β-synthase catalyzes a PLP-dependent condensation of serine and homocysteine to cystathionine and is unique in also having a heme cofactor.

How is cystathionine synthesized from osuccinyl-L-homoserine?

Cystathionine gamma-synthase catalyzes a pyridoxal phosphate dependent synthesis of cystathionine from O-succinyl-L-homoserine (OSHS) and L-cysteine via a gamma-replacement reaction. In the absence of L-cysteine, OSHS undergoes an enzyme-catalyzed, gamma-elimination reaction to form succinate, alpha …

Can cystathionine γ-lyase catalyze β-elimination reactions?

Although cystathionine γ-lyase normally catalyzes a γ-elimination reaction, it can also catalyze β-elimination reactions that may be physiologically relevant.