Folatcyklusen

Folatcyklusen, also known as the folate cycle or one-carbon metabolism, is a crucial biochemical pathway in all living organisms. It involves the interconversion of folate derivatives, which serve as essential coenzymes for a variety of metabolic reactions. The primary role of folate derivatives is to carry and transfer one-carbon units (such as methyl, formyl, and methylene groups) in biosynthetic processes.

The cycle begins with the uptake of dietary folate, primarily in the form of pteroylglutamate, which is then converted to dihydrofolate and subsequently to tetrahydrofolate (THF). THF is the principal active form of folate. In a series of reactions, THF can be modified to carry different one-carbon units. For instance, 5,10-methylenetetrahydrofolate is vital for the synthesis of thymidylate, a key component of DNA. 10-formyltetrahydrofolate is essential for purine synthesis, another fundamental building block of nucleic acids.

Furthermore, the folate cycle is intimately linked with the metabolism of amino acids, particularly methionine and serine. The conversion of 5-methyltetrahydrofolate back to THF is coupled with the remethylation of homocysteine to methionine, a reaction catalyzed by methionine synthase. This process is critical for maintaining adequate levels of methionine for protein synthesis and for the regeneration of S-adenosylmethionine, a universal methyl group donor.

Disruptions in the folate cycle can have significant health consequences, leading to a range of disorders. For example, deficiencies in folate can impair DNA synthesis and repair, contributing to megaloblastic anemia and neural tube defects in developing fetuses. Understanding the intricacies of the folate cycle is therefore essential for comprehending various physiological processes and for developing therapeutic strategies for related diseases.