The ring is closed after the formation of a ketose. The overall reaction causes the ring to form an aldose through acid/base catalysis and then subsequently forms cis-ethanol intermediate. ring-opening and contraction of the ring is the isomerisation of glucose to fructose. Ring Expansion And Contraction Via Tautomers:Īn example of this kind of mechanism, i.e. Some of the reactions catalysed by intramolecular lyases involve the breaking of the ring structure. Intramolecular lyases function in reactions where a group is considered to be removed from one part of the molecule that forms a double bond while still being covalently attached to the molecule. The intramolecular transferases can be sub-classified down depending on which functional group the enzyme moves. Intramolecular transferases (mutases) are used to catalyse the movement of functional groups from one part of the molecule to another. Depending on their processes intramolecular oxidoreductases can be divided into further sib-classes. Simply put, they catalyse the reaction that oxidises one part of the molecule while reducing the other part. These isomerases function by catalysing the transfer of electrons from one molecule to the other. This class is not broken down further into sub-classes. The difference between cis-trans isomers is that cis isomers have their substituent groups on the same side while the trans isomers have their groups on opposite sides. These isomers are distinguished through the positioning of the substituent groups relative to that of the plane of reference instead of absolute configuration. Certain alkenes and cycloalkanes could have cis-trans stereoisomers. This class is for the isomerases that catalyse the isomerization of the cis-trans isomers. This category is then further broken down depending on what the enzyme acts upon, for example, action on amino acids or carbohydrates. While racemases act on molecules with one chiral carbon, the epimerases act on molecules with multiple chiral carbons but act only one of them. The racemases and epimerases function by inverting stereochemistry at the target chiral carbon. The isomerase can then be further categorised into six sub-classes: 1. The enzyme classification category for isomerase-catalysed reactions is EC 5. Classification Of Isomerases:Įnzyme catalysed reactions are known to have their own unique classification number. The stereoisomers are catalysed using racemases, epimerases and cis-trans isomers. On the other hand, stereoisomers have the same order of individual bonds and even the same connectivity but there is a difference in three-dimensional arrangement of the bonds. Structural isomers can be catalysed by intramolecular lyases, oxidoreductases and transferases. In structural isomers, the bonds are ordered differently or they differ in their bond connectivity from one other. Even though there are many different existing varieties of isomers they can be classified into two different groups-structural isomers and stereoisomers. Since they change one isomer to another, the end product has the same molecular formula but an alternate physical structure. The isomerases function by catalysing changes within just one molecule. Glycolysis and carbohydrate metabolism are a couple of examples for the same. The isomerases are known to catalyse many different biological reactions. Even though the product and the substrate have the same molecular formula, they have different bond connectivity and spatial arrangement. There is a singular substrate which also produces just one product. Intramolecular rearrangements are where bonds are broken and formed. They typically make intramolecular rearrangements easier. The enzyme isomerase is a general class of enzymes that can change a molecule from one isomer to others.
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