Term: constitutive enzymes https://doi.org/10.1351/goldbook.C01289 Definition: enzymes which are produced constitutively by the cell under all physiological conditions. Therefore, they are not controlled by induction or repression. Related Terms: 1) enzymes (http://doi.org/10.1351/goldbook.E02159). 2) induction (http://doi.org/10.1351/goldbook.I03018). 3) repression (http://doi.org/10.1351/goldbook.R05304). Source: PAC, 1992, 64, 143. 'Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)' on page 150 (https://doi.org/10.1351/pac199264010143) Citation: 'constitutive enzymes' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.C01289 License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.