An adaptive enzyme or inducible enzyme is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

that is expressed only under conditions in which it is clearly of adaptive value, as opposed to a

constitutive enzyme Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. Th ...

which is produced all the time. The inducible enzyme is used for the breaking-down of things in the cell. It is also a part of the Operon Model, which illustrates a way for genes to turn "on" and "off". The inducer causes the gene to turn on (controlled by the amount of reactant which turns the gene on). Then there's the repressor protein that turns genes off. The inducer can remove this repressor, turning genes back on. The operator is a section of DNA where the repressor binds to shut off certain genes; the promoter is the section of DNA where the

RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...

binds. Lastly, the regulatory gene is the gene for the repressor protein. An example of inducible enzyme is COX-2 which is synthesized in

macrophages Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer ce ...

to produce prostaglandin E₂ while the

COX-1 (another isozyme in COX family) is always produced in variety of organs in body (like stomach).

References

Enzymes {{Enzyme-stub