singlesubstrate

Singlesubstrate is a term used in chemistry and biochemistry to describe reactions in which only a single substrate participates directly in the catalytic turnover. The term is typically applied to enzyme-catalyzed transformations where one primary substrate is converted to a product, as opposed to reactions that require two or more substrates to bind or react in the rate-determining step. In practice, the phrase is sometimes written as single-substrate, and its precise meaning can vary by field.

In enzymology, single-substrate reactions often obey Michaelis–Menten kinetics under steady-state conditions. The rate is commonly described by v = Vmax [S]/(Km + [S]), where S is the primary substrate. In these descriptions, cofactors or cosubstrates may be essential for activity but are not always counted as substrates in the same kinetic expression; the primary substrate is the species being transformed. This contrasts with multisubstrate mechanisms, such as ordered, random, or ping-pong processes, where the rate law depends on more than one substrate.

Applications and examples: The singlesubstrate framework simplifies kinetic analysis and is widely used for characterizing enzyme affinity and turnover. It is also encountered in chemical catalysis and materials science when a catalyst transforms a single reactant. Researchers use single-substrate studies to determine parameters like Km and kcat, to compare catalysts, or to design inhibitors that target the substrate binding site.

Notes: The term is not uniformly standardized across disciplines; readers should check contextual definitions in specific sources. See also Michaelis–Menten kinetics and multisubstrate mechanisms.