| enzyme | <biochemistry> A protein molecule produced by living organisms that catalyses chemical reactions of other substances without itself being destroyed or altered upon completion of the reactions. Enzymes are classified according to the recommendations of the Nomenclature Committee of the International Union of Biochemistry. Each enzyme is assigned a recommended name and an Enzyme Commission (EC) number. They are divided into six main groups, oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases. (09 Oct 1997) |
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| enzyme activation | Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1) activation by ions (activators); 2) activation by cofactors (coenzymes); and 3) conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. (12 Dec 1998) |
| enzyme analog | A synthetic macromolecule having enzymatic activity. Synonym: enzyme analog. (05 Mar 2000) |
| enzyme antagonist | An antimetabolite or inhibitor of enzyme action. (05 Mar 2000) |
| enzyme defect | A disorder resulting from a deficiency (or functional abnormality) of an enzyme. In 1902 Archibald Garrod first attributed a disease to an enzyme defect: an inborn error of metabolism. Today, newborns are routinely screened for certain enzyme defects such as PKU (phenylketonuria) and galactosaemia, an error in the handling (metabolism) of the sugar galactose. (12 Dec 1998) |
| enzyme derepression | Removing or turning off the inhibitor or inhibitors (molecules which repress or prevent other molecules from acting) enzyme so that enzyme activity can resume. (09 Oct 1997) |
| enzyme electrode | A type of biosensor. An enzyme is immobilised on the surface of an electrode, and when the enzyme catalyses its reaction, electrons are transferred from the reactant to the electrode, and a current is generated, which can then be measured. (14 Nov 1997) |
| enzyme immobilisation | The attachment of an enzyme to a solid matrix so that it cannot escape but can still act on its substrate. (09 Oct 1997) |
| enzyme immunoassay | The general term for an expanding technical arsenal of testing which allows a full range of quantitative analyses for both antigen and antibodies. These tests use colour-changed products of enzyme-substrate interaction (or inhibition) to measure the antigen-antibody reaction. Examples of EIA procedures (EMIT, ELISA, MAC, MEIA) follow. Acronym: EIA (05 Mar 2000) |
| enzyme inactivation | The disappearance of an enzyme's activity during in vitro conditions, such as during a lab preparation of the enzyme, where the enzyme is exposed to conditions not normally found within its environment inside a living cell (like different pH, excess or too little salt, temperature changes, etc.) (09 Oct 1997) |
| enzyme induction | An increase in enzyme secretion in response to an environmental signal. The classic example is the induction of _ galactosidase in E. Coli. (18 Nov 1997) |
| enzyme inhibition theory of narcosis | That narcotics inhibit respiratory enzymes by suppression of the formation of high energy phosphate bonds within the cell. (05 Mar 2000) |
| enzyme inhibitors | Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction. (12 Dec 1998) |
| enzyme precursor | <biochemistry> Inactive precursors that can be converted to active enzymes. Enzyme precursors containing extra-long polypeptide chains that block activity are activated by acid or enzymatic hydrolysis to remove the inhibiting portion. (12 Dec 1998) |
| enzyme reactivator | <biochemistry> Compounds which restore enzymatic activity by removing an inhibitory group bound to the reactive site of the enzyme. (12 Dec 1998) |
| acetyl-activating enzyme | A ligase that catalyses the reaction of acetate and CoA and ATP to form AMP, pyrophosphate, and acetyl-CoA. A key step in the activation of acetate. Synonym: acetate thiokinase, acetate-CoA ligase, acetyl-activating enzyme, acetyl-CoA synthetase. (05 Mar 2000) |
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| acyl-activating enzyme | <enzyme> Fatty acid thiokinase (long-chain), a ligase forming acyl-CoA, AMP, and pyrophosphate from long-chain fatty acids, ATP, and coenzyme A. Activity is independent of phosphatidylcholine Registry number: EC 6.2.1.3 Synonym: acyl-activating enzyme, dodecanoyl-CoA synthetase, fatty acid thiokinase (long chain), acid-coenzyme a ligase, fatty acid-CoA ligase, acyl-CoA synthetase, acyl-CoA ligase, coash ligase, ciprofibroyl-CoA synthetase, pristanoyl-CoA synthetase, palmityl CoA synthetase, palmitoyl CoA synthetase, palmitoyl CoA ligase, fatty acyl-CoA synthetase, very long chain fatty acid acyl-CoA synthetase, vlcfa acyl-CoA synthetase, nafenopin-CoA ligase, palmitoyl-CoA synthase, faa2 gene product, faa2p protein, vlacs enzyme (26 Jun 1999) |
| adaptive enzyme | Inducible enzyme, an enzyme that can be detected in a growing culture of a microorganism, after the addition of a particular substance (inducer) to the culture medium, but was not detectable prior to the addition and can act on the inducer. A prototype is the beta-galactosidase of Escherichia coli, synthesised upon the addition of various galactosides, whether or not these are good substrates. Compare: constitutive enzyme. Synonym: adaptive enzyme. (05 Mar 2000) |
| allosteric enzyme | <biochemistry, chemistry> A regulatory enzyme whose activity is modified by the noncovalent binding of a particular metabolite at a site (the allosteric site) other than the active site. (09 Oct 1997) |
| amino acid activating enzyme | <enzyme> Enzymes catalyzing the formation of a specific aminoacyl-tRNA from an amino acid and adenosine 5'-triphosphate with the concomitant formation of adenosine 5'-monophosphate and pyrophosphate. Synonym: amino acid activating enzyme, aminoacyl-tRNA ligases. (05 Mar 2000) |
| angiotensin-converting enzyme | <enzyme> This hydrolase enzyme cleaves the decapeptide angiotensin I (biologically inactive) to form active angiotensin II by angiotensin-converting enzyme which removes a dipeptide (histidylleucine) from angiotensin I. Angiotensin II causes contraction of vascular smooth muscle and thus raises blood pressure and stimulates aldosterone release from the adrenal glands. Angiotensin is finally broken down by angiotensinases. Elevations in angiotensin converting enzyme are seen sarcoidosis, histoplasmosis, alcoholic cirrhosis, asbestosis, berylliosis, diabetes, Hodgkin's disease, hyperthyroidism, amyloidosis, primary biliary cirrhosis, idiopathic pulmonary fibrosis, pulmonary embolism, scleroderma, silicosis, tuberculosis, Gaucher's disease and leprosy. The normal values are 18 to 67 U/ml over 20 years of age (people under 20 have higher levels). Drugs that inhibit ACE are used to treat hypertension and congestive heart failure. See: angiotensin-converting enzyme inhibitor Acronym: ACE (12 Aug 2000) |
| angiotensin-converting enzyme inhibitor | <pharmacology> A class of drugs used in the treatment of hypertension and heart failure. They exert their haemodynamic effect mainly by inhibiting the renin-angiotensin system and produce a reduction of peripheral arterial resistance. They also modulate sympathetic nervous system activity and increase prostaglandin synthesis. They cause mainly vasodilation and mild natriuresis without affecting heart rate and contractility. (14 Aug 2000) |
| angiotensin-converting enzyme secretase | <enzyme> Converts ace from a membrane-bound to a soluble form; not inhibited by thiol, serine or acid enzyme inhibitor but is inhibited by edta and 1,10-phenanthroline Registry number: EC 3.4.99.- Synonym: ace secretase (26 Jun 1999) |
| Antibody Directed Enzyme Prodrug Therapy | <pharmacology> A method for targeting a drug to a specific tissue, in which the targeting agent and the drug are administered separately. The drug is designed to be inactive (a prodrug) until it is converted by an enzyme, which is the targeting agent. The enzyme is coupled to an antibody that directs it to the tissue of interest. When the enzyme arrives at the tissue, the prodrug is activated only at that site, sparing other tissues from potentially toxic side effects. Acronym: ADEPT (14 Nov 1997) |
| antitumour enzyme | <enzyme> An enzyme that stimulates the degradation of a particular metabolite that cannot be synthesised by tumour cells, inhibits the synthesis of a metabolite needed by tumour cells, or inhibits tumour-specific DNA utilization; e.g., asparaginase. (05 Mar 2000) |
| autolytic enzyme | <enzyme> An enzyme capable of causing lysis of the cell forming it. (05 Mar 2000) |
| beta-carotene cleavage enzyme | <enzyme> An enzyme catalyzing the reaction of beta-carotene plus O2 producing two retinals. Synonym: beta-carotene cleavage enzyme, carotenase, carotinase. (05 Mar 2000) |
| branching enzyme | 1,4-alpha-d-glucan branching enzyme |
| cardiac enzyme | <biochemistry> A group of enzymes found normally in heart tissue. Cardiac enzymes are released into the blood stream in increased concentration when the heart muscle becomes damaged. Examples include SGOT, CPK-MB and LDH. (27 Sep 1997) |
| pancreatic enzyme | <biochemistry> One of the proteins made by the pancreas that aid digestion of fats, carbohydrates and proteins. (09 Oct 1997) |