kofaktoridena

Cofactors are non‑protein chemical compounds or metallic ions that bind to enzymes and are essential for their biological activity. They can be classified into two main categories: organic coenzymes, which are derived from vitamins or other metabolic intermediates, and inorganic cofactor groups, which are often metal ions such as iron, zinc, magnesium, or copper. Some cofactors form covalent, non‑covalent, or transient associations with the protein. Cofactors may act as electron carriers, participate in substrate binding, provide catalytic groups, or stabilize the enzyme structure.

Organic cofactors, known as coenzymes, include nicotinamide adenine dinucleotide (NAD⁺/NADP⁺), flavin adenine dinucleotide (FAD), coenzyme A, and many others. These molecules cycle between oxidized and reduced forms and thereby mediate redox reactions, acyl transfer, and other essential biochemical transformations. Vitamin B₁₂ and thiamine pyrophosphate are classic examples of coenzyme prosthetic groups that remain tightly bound to the enzyme throughout the catalytic cycle.

Inorganic metal ions often occupy sites in metalloenzymes. For instance, the iron atom in cytochromes allows electron transfer, whereas zinc in carbonic anhydrase stabilizes the transition state of the hydration of carbon dioxide. Magnesium ions are critical for ATP binding in many kinases and polymerases, acting as a counterion to the negative charges on phosphate groups.

Cofactors are indispensable for metabolic pathways, including glycolysis, the citric acid cycle, oxidative phosphorylation, DNA replication, and protein synthesis. Deficiencies in cofactors, whether due to nutritional deficits or genetic mutations that affect their synthesis or utilization, can lead to a range of metabolic disorders. Thus, the proper supply and regulation of cofactors are vital for cellular homeostasis and organismal health.