Cystathionase

Definition: Cystathionase is an enzyme that plays a crucial role in the metabolism of the amino acid methionine, specifically in the transsulfuration pathway.

Function

The main function of cystathionase is to catalyze the conversion of cystathionine, a compound formed during the methionine metabolism, into cysteine and α-ketobutyrate. This enzyme is responsible for the last step of the transsulfuration pathway, which is essential for the synthesis of cysteine, an important sulfur-containing amino acid.

Importance in Metabolism

Cystathionase plays a vital role in maintaining the balance of sulfur-containing amino acids in the body. It ensures the steady production of cysteine, which is necessary for several physiological processes, including protein synthesis and the synthesis of important biomolecules like glutathione. Additionally, the transsulfuration pathway, where cystathionase functions, contributes to the removal of excess sulfur from methionine metabolism.

Regulation

The activity of cystathionase is regulated by various factors, including the availability of cofactors such as pyridoxal phosphate (PLP) and the concentration of substrate molecules like cystathionine. Furthermore, genetic variations and mutations in the CTH gene, which encodes cystathionase, can affect the enzyme’s activity and lead to metabolic disorders such as homocystinuria.

Medical Relevance

Deficiency or dysfunction of cystathionase can result in metabolic disorders characterized by abnormal accumulation of homocysteine and cystathionine in the body. Homocystinuria, one such disorder, can lead to various symptoms, including intellectual disability, skeletal abnormalities, and increased risk of cardiovascular problems. Understanding the role of cystathionase in these disorders helps in developing diagnostic methods and potential therapeutic interventions.