Enzymes
| Definition: |
Biological molecules that possess catalytic activity. They may occur naturally or be synthetically created. Enzymes are usually proteins, however catalytic RNA (RNA, CATALYTIC) and catalytic DNA (DNA, CATALYTIC) molecules have also been identified. |
| Notes: |
GEN only: avoid; prefer /enzymol: Manual 19.7+, 19.8.30; /defic permitted but specific enzyme /defic is more likely; /diag use: very unlikely: probably incorrect for ENZYME TESTS; Manual 23.25.1; policy: Manual 25.19+; index enzyme substrate as NIM withou |
| Also Called: |
Enzymatic Effects |
Enzymes Categories.
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DNA Repair Enzymes - Enzymes that are involved in the reconstruction of a continuous two-stranded DNA molecule without mismatch from a molecule, which contained damaged regions. |
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DNA Restriction-Modification Enzymes - Systems consisting of two enzymes, a modification methylase and a restriction endonuclease. They are closely related in their specificity and protect the DNA of a given bacterial species. The methylase adds methyl groups to adenine or cytosine residues in the same target sequence that constitutes the restriction enzyme binding site. The methylation renders the target site resistant to restriction, thereby protecting DNA against cleavage. |
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DNA, Catalytic - Molecules of DNA that possess enzymatic activity. |
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Enzymes, Immobilized - Enzymes which are immobilized on or in a variety of water-soluble or water-insoluble matrices with little or no loss of their catalytic activity. Since they can be reused continuously, immobilized enzymes have found wide application in the industrial, medical and research fields. |
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Holoenzymes - Catalytically active enzymes that are formed by the combination of an apoenzyme (APOENZYMES) and its appropriate cofactors and prosthetic groups. |
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Hydrolases - Any member of the class of enzymes that catalyze the cleavage of the substrate and the addition of water to the resulting molecules, e.g., ESTERASES, glycosidases (GLYCOSIDE HYDROLASES), lipases, NUCLEOTIDASES, peptidases (PEPTIDE HYDROLASES), and phosphatases (PHOSPHORIC MONOESTER HYDROLASES). EC 3. |
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Isoenzymes - One of various structurally related forms of an enzyme, each having the same mechanism but with differing chemical, physical, or immunological characteristics. |
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Isomerases - A class of enzymes that catalyze geometric or structural changes within a molecule to form a single product. The reactions do not involve a net change in the concentrations of compounds other than the substrate and the product.(from Dorland, 28th ed) EC 5. |
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Ligases - A class of enzymes that catalyze the formation of a bond between two substrate molecules, coupled with the hydrolysis of a pyrophosphate bond in ATP or a similar energy donor. (Dorland, 28th ed) EC 6. |
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Lyases - A class of enzymes that catalyze the cleavage of C-C, C-O, and C-N, and other bonds by other means than by hydrolysis or oxidation. (Enzyme Nomenclature, 1992) EC 4. |
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Multienzyme Complexes - Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates; may involve simply a transfer of water molecules of hydrogen atoms or be associated with large supramolecular structures such as mitochondria or ribosomes. |
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Oxidoreductases - The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9) |
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Recombinases - A broad category of enzymes that are involved in the process of GENETIC RECOMBINATION. |
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RNA, Catalytic - RNA that has catalytic activity. The catalytic RNA sequence folds to form a complex surface that can function as an enzyme in reactions with itself and other molecules. It may function even in the absence of protein. There are numerous examples of RNA species that are acted upon by catalytic RNA, however the scope of this enzyme class is not limited to a particular type of substrate. |
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Transferases - Transferases are enzymes transferring a group, for example, the methyl group or a glycosyl group, from one compound (generally regarded as donor) to another compound (generally regarded as acceptor). The classification is based on the scheme "donor:acceptor group transferase". (Enzyme Nomenclature, 1992) EC 2. |
Enzymes Definitions and Terms
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