Promoter

promoter

1. Chem a substance added in small amounts to a catalyst to increase its activity

2. Genetics a sequence of nucleotides, associated with a structural gene, that must bind with messenger RNA polymerase before transcription can proceed

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promoter [prə′mōd·ər]

(chemistry)

A chemical which itself is a feeble catalyst, but greatly increases the activity of a given catalyst.

(genetics)

The site on deoxyribonucleic acid to which ribonucleic acid polymerase binds preparatory to initiating transcription of a gene or an operon.

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catalyst

1. A substance which accelerates a chemical reaction but appears to remain unchanged itself.

2. A hardener that accelerates cure of adhesives either with or without heat. Used primarily with synthetic resins.

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Promoter 

a substance added to a catalyst in order to increase its activity, selectivity, or stability. A promoted catalyst is usually a catalyst containing a small amount of a promoter that by itself is catalytically inactive or only slightly active. In the case where the promoter is not inactive, the addition creates a mixed catalyst. Often an additive, given certain external conditions, concentrations, and methods of addition, acts as a promoter, whereas under different conditions the same additive serves as a catalyst poison. Most commercial catalysts belong to the promoted category. For example, V₂O_s, the catalyst which speeds up the oxidation of SO₂ into SO₃, is promoted by the oxides of alkali metals; metallic Fe, which catalyzes the synthesis of ammonia, is promoted by the oxides of aluminum, calcium, potassium, and other metals. The mechanism involved in the activity of promoters is explained by modern theories of catalysis.