Canadian Medical Guide > Chemicals and Drugs > Enzymes and Coenzymes > Enzymes > Isomerases Terms and Definitions

Isomerases

Medical Definition:	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.
Guide Notes:	GEN only; see Tree D8 under ISOMERASES & choose the most specific
CAS Number:	EC 5.

Isomerases Categories.

	cis-trans-Isomerases - Enzymes that catalyze the rearrangement of geometry about double bonds. EC 5.2.
	DNA Helicases - Proteins that promote unwinding of duplex DNA during replication by binding cooperatively to single-stranded regions of DNA or to short regions of duplex DNA that are undergoing transient opening. EC 5.99.-.
	DNA Topoisomerases - Enzymes that regulate the topology of DNA by actions such as breaking, relaxing, passing, and rejoining strands of DNA in cells. These enzymes are important components of the DNA replication system. They are classified by their substrate specificities. DNA TOPOISOMERASE, TYPE I enzymes act on a single strand of DNA. DNA TOPOISOMERASE, TYPE II enzymes act on double strands of DNA.
	Intramolecular Lyases - Enzymes of the isomerase class that catalyze reactions in which a group can be regarded as eliminated from one part of a molecule, leaving a double bond, while remaining covalently attached to the molecule. (From Enzyme Nomenclature, 1992) EC 5.5.
	Intramolecular Oxidoreductases - Enzymes of the isomerase class that catalyze the oxidation of one part of a molecule with a corresponding reduction of another part of the same molecule. They include enzymes converting aldoses to ketoses (ALDOSE-KETOSE ISOMERASES), enzymes shifting a carbon-carbon double bond (CARBON-CARBON DOUBLE BOND ISOMERASES), and enzymes transposing S-S bonds (SULFUR-SULFUR BOND ISOMERASES). (From Enzyme Nomenclature, 1992) EC 5.3.
	Intramolecular Transferases - Enzymes of the isomerase class that catalyze the transfer of acyl-, phospho-, amino- or other groups from one position within a molecule to another. EC 5.4.
	Racemases and Epimerases - Enzymes that catalyze inversion of the configuration around an asymmetric carbon in a substrate having one (racemase) or more (epimerase) center(s) of asymmetry. (Dorland, 28th ed) EC 5.1.

Isomerases Medical Definitions and Terms

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