substratkoncentration

Substratkoncentration, or substrate concentration, refers to the amount of substrate present in a reaction mixture per unit volume and is a fundamental variable in enzymology. It determines how much substrate is available for an enzyme to convert into product.

In Michaelis–Menten kinetics, the reaction velocity v is a function of the substrate concentration [S]. At low [S], the rate increases approximately linearly with [S]; at high [S], the rate approaches a maximum value, Vmax. The relationship is described by v = (Vmax [S])/(Km + [S]), where Km is the substrate concentration at half-maximal velocity and reflects the enzyme’s affinity for the substrate.

Substrate concentration is typically expressed in molarity (moles per liter, M). In laboratory experiments, [S] is varied to characterize kinetics and estimate Km and Vmax. Practical considerations include maintaining assay conditions (pH, temperature) and accounting for substrate consumption, product inhibition, and transporter effects that can alter the effective [S] during the reaction.

Deviation from Michaelis–Menten behavior can occur. At very high [S], some enzymes show substrate inhibition; allosteric enzymes may display cooperative binding, causing sigmoidal velocity curves. In cells, substrate availability, transport across membranes, and compartmentalization influence the effective substrate concentration and metabolic flux.

Measurement and interpretation: Substrate concentration is determined and controlled as part of kinetic experiments, often using spectrophotometric assays, coupled reactions, or chromatographic methods. Data are analyzed with Michaelis–Menten or Hill equations to derive kinetic parameters such as Km and Vmax.