catalyst

(kăt′ă-lĭst )

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A substance that speeds the rate of a chemical reaction without being permanently altered in the reaction. Catalysts are effective in small quantities and are not used up in the reaction, i.e., they can be recovered unchanged. All enzymes are catalysts; the human body has thousands of enzymes, each specific for a particular reaction. For example, pepsin catalyzes the hydrolysis of protein; amylase catalyzes the hydrolysis of starch; transaminases catalyze the transfer of an amino group from one molecule to another.
SYN: SEE: catalyzer

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