Substrate (biochemistry)

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In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate(s). The substrate binds with the enzyme's active site, and an enzyme-substrate-complex is formed. The substrate is broken down into a product and is released from the active site. The active site is now free to accept another substrate molecule. An example of a substrate would be milk and the enzyme added would be rennin which causes milk to set. Another example would be the reaction of catalase in the decomposition of hydrogen peroxide.

2 H2O2 → 2 H2O + O2.

A general equation is as follows:

E + S ⇌ ES → EP ⇌ E + P

where E = enzyme, S = substrate(s), P = product(s) Note that only the middle step is irreversible.

The reaction follows Michaelis-Menten kinetics.