cosubsztrát

Cosubstrate is a term used in chemistry and biochemistry to describe a substance that is required for an enzyme to catalyze a reaction but is not a substrate itself. It is a molecule that participates in the reaction but is not consumed in the process. Cosubstrates are often involved in redox reactions or in the transfer of specific chemical groups. They can be either organic or inorganic molecules.

Examples of cosubstrates include molecules like NAD+ (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide), which act as electron carriers in many metabolic pathways. These molecules accept or donate electrons during enzymatic reactions, thereby facilitating the overall transformation of the actual substrate. Other cosubstrates might be involved in transferring phosphate groups or other functional moieties.

Unlike coenzymes, which are typically organic molecules that bind loosely to enzymes and are regenerated after each reaction cycle, cosubstrates can sometimes be consumed or permanently altered during the reaction, though their primary role is facilitative rather than being a direct reactant broken down into products. The distinction can sometimes be subtle, and the terms are occasionally used interchangeably, but the core concept of a non-substrate participant in an enzymatic reaction remains central to the definition of a cosubstrate. They are essential for the enzyme's function, enabling it to achieve its catalytic activity efficiently.