Methionine is an essential amino acid in humans. As the precursor of other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical role in the metabolism and health of many species, including humans. It is encoded by the codon AUG.
Cystathionine-β-synthase, also known as CBS, is an enzyme (EC 4.2.1.22) that in humans is encoded by the CBS gene. It catalyzes the first step of the transsulfuration pathway, from homocysteine to cystathionine:
The enzyme cystathionine γ-lyase (EC 4.4.1.1, CTH or CSE; also cystathionase; systematic name L-cystathionine cysteine-lyase (deaminating; 2-oxobutanoate-forming)) breaks down cystathionine into cysteine, 2-oxobutanoate (α-ketobutyrate), and ammonia:
The transsulfuration pathway is a metabolic pathway involving the interconversion of cysteine and homocysteine through the intermediate cystathionine. Two transsulfurylation pathways are known: the forward and the reverse.
Cystathionine beta-lyase, also commonly referred to as CBL or β-cystathionase, is an enzyme that primarily catalyzes the following α,β-elimination reaction
The enzyme cysteine lyase catalyzes the chemical reaction
The enzyme D-cysteine desulfhydrase (EC 4.4.1.15) catalyzes the chemical reaction
The enzyme methionine γ-lyase (EC 4.4.1.11, MGL) is in the γ-family of PLP-dependent enzymes. It degrades sulfur-containing amino acids to α-keto acids, ammonia, and thiols:
The enzyme selenocysteine lyase (SCL) (EC 4.4.1.16) catalyzes the chemical reaction
In enzymology, a 3-mercaptopyruvate sulfurtransferase is an enzyme that catalyzes the chemical reactions of 3-mercaptopyruvate. This enzyme belongs to the family of transferases, specifically the sulfurtransferases. This enzyme participates in cysteine metabolism. It is encoded by the MPST gene.
The enzyme anthranilate synthase catalyzes the chemical reaction
The enzyme hydroxymandelonitrile lyase catalyzes the chemical reaction
In enzymology, a hydroxynitrilase is an enzyme that catalyzes the chemical reaction
The enzyme (R)-mandelonitrile lyase (EC 4.1.2.10, (R)-HNL, (R)-oxynitrilase, (R)-hydroxynitrile lyase) catalyzes the chemical reaction
In enzymology, an aminodeoxychorismate synthase is an enzyme that catalyzes the chemical reaction
The enzyme 3-cyanoalanine hydratase (EC 4.2.1.65) catalyzes the chemical reaction
In enzymology, a malate synthase (EC 2.3.3.9) is an enzyme that catalyzes the chemical reaction
In enzymology, a cystathionine gamma-synthase is an enzyme that catalyzes the formation of cystathionine from cysteine and an activated derivative of homoserine, e.g.:
In enzymology, a cysteine synthase is an enzyme that catalyzes the chemical reaction
In enzymology, an O-phosphoserine sulfhydrylase is an enzyme that catalyzes the chemical reaction
