Enzyme induction

Enhancement of enzyme synthesis through positive gene regulation, i.e. activation of the expression and activity of certain genes to adapt biochemical reactions to a given situation. Gene regulation can take place at the DNA, RNA or protein level (synthesis of the enzyme). Inductors of various kinds are used to increase the mRNA synthesis and thus, at the protein level, the biosynthesis of the enzyme.

Enzyme inducers can be endogenous or exogenous substances. The induction can be made by the active substance itself (autoinduction) or by a foreign active substance (external induction). It may be reversible or irreversible. Tolerance may arise if the inductor is applied repeatedly.

The process of enzyme induction can be illustrated using the growth of bacterial colonies as an example: If there is lactose in the cell of E. coli, for example, lactose binds to the repressor, which is inactivated by this. This allows the RNA polymerase to become active and synthesizes various enzymes for the degradation of lactose. In the absence of lactose in the cell, the repressor binds directly to a so-called operator. This inhibits or stops the transcription process and thus the enzyme synthesis. The process of gene regulation ensures an economic use of resources. The lactose-degrading enzymes are only produced when there is lactose in the cell.

Hormones, cytokines, drugs such as barbiturates, rifampicin and St. John's wort can, for example, act as inducers of cytochrome P450-dependent monooxygenases. This process leads e.g. to an increased clearance of drugs that are degraded by cytochrome P450 enzymes and to their reduced efficacy (e.g. in the case of Ciclosporin A).