What is enzyme kinetics

Catalysts are defined as substances that participate in a chemical reaction but are not changed or consumed. Instead they provide a new mechanism for a reaction to occur which has a lower activation energy than that of the reaction without the catalyst. Homogeneous catalysis refers to reactions in which the catalyst is in solution with at least one of the reactants whereas heterogeneous catalysis refers t Enzymes are high-molecular weight proteins that act on a substrate, or reactant molecule, to form one or more products.

Enzymes are highly specific catalysts for biochemical reactions, with each enzyme showing a selectivity for a single reactant, or substrate. It uses an active serine residue to perform hydrolysis on the C-terminus of the aromatic amino acids of other proteins. Chymotrypsin is a protease enzyme that cleaves on the C-terminal phenylalanine F , tryptophan W , and tyrosine Y on peptide chains.

It shows specificity for aromatic amino acids because of its hydrophobic pocket. Enzymatic reactions requiring multiple substrates and yielding multiple products are more common and yielding multiple products are more common than single-substrate reaction. In these types of reactions, the all the substrates involved are bound to the enzyme before catalysis of the reaction takes place to release the products. In some cases of enzyme inhibition, for example, an inhibitor molecule is similar enough to a substrate that it can bind to the active site and simply block the substrate from binding.

Enzymes are protein catalysts, they influence the kinetics but not the thermodynamics of a reaction. Figure 6. The Michaelis-Menten equation is a mathematical model that is used to analyze simple kinetic data. The model has certain assumptions , and as long as these assumptions are correct, it will accurately model your experimental data.

The derivation of the model will highlight these assumptions. In an enzyme catalyzed reaction the substrate initially forms a reversible complex with the enzyme i. The standard expression to show this is the following:. The rate of ES breakdown is a combination of the dissociation and the conversion to product:. This is the mathematical expression that is used to model your experimental kinetic data. The general approach is to add a known concentration of substrate to the enzyme and to determine the initial reaction rate for that concentration of substrate.

There are a limited number of enzyme molecules and they can only perform a single reaction at a time. Thus, at high [S] the enzymes can be saturated. There is a mathematical treatment that allows for the determination of Km from the experimental V versus [S] data.

Thus, K m equals the substrate concentration that results in exactly one half the maximum possible reaction velocity. There are two major categories of reversible inhibitors: competitive reversible inhibitors, and noncompetitive reversible inhibitors:. The inhibitor I competes with the substrate S for the enzyme active site also known as the S-binding site.