Cofactor

A cofactor is a non-protein chemical compound or metallic ion that is required by an enzyme for the enzyme to catalyze a biochemical reaction. Cofactors can be either inorganic (e.g., metal ions like zinc, magnesium, or iron) or organic. When an organic cofactor is tightly bound to an enzyme, it is often called a prosthetic group. They assist in enzyme function, participating directly in the reaction, or facilitating substrate binding. The presence or absence of a specific cofactor can significantly influence the rate and specificity of enzymatic activity, thereby playing a critical role in metabolic pathways.

Cofactor meaning with examples

• 1. The enzyme, catalase, requires a heme group (containing iron) as a cofactor to break down hydrogen peroxide. Without this cofactor, catalase is inactive and cannot perform its essential function. This highlights the critical role of cofactors in enzymatic processes.
• 2. In glycolysis, magnesium ions act as cofactors for several enzymes involved in ATP production. The metal ions neutralize the negative charges on phosphate groups, facilitating substrate binding and the transfer of phosphate molecules. Therefore, a lack of magnesium can disrupt glycolysis.
• 3. Certain enzymes involved in amino acid metabolism need pyridoxal phosphate (derived from vitamin B6) as a cofactor to carry out transamination reactions, the process which allows for interconversion of amino acids. This vitamin helps catalyze this transfer in an essential metabolic pathway.
• 4. DNA polymerase relies on magnesium ions as cofactors to stabilize the negatively charged phosphate groups of the incoming nucleotides and the active site of the polymerase enzyme, aiding in accurate DNA replication. Thus, the cofactor is an indispensable tool of the enzyme.
• 5. Some dehydrogenases require nicotinamide adenine dinucleotide (NAD+) as a cofactor. NAD+ accepts electrons and hydrogen atoms from substrates, transferring them in the form of NADH during redox reactions. The redox reactions, in turn, will use the energy produced for work.