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Isozyme
Isozymes are multiple forms of the same enzyme that catalyze the same chemical reaction but have different chemical and physical properties. Enzyme regulation can occur through various mechanisms, including changing enzyme production levels, compartmentalizing metabolic pathways in different cell locations, and post-translational modifications. Common regulatory mechanisms include cyclic phosphorylation/dephosphorylation of proteins and allosteric regulation where binding of an effector molecule like an end product induces a conformational change that increases or decreases the enzyme's activity level.
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Isozyme
- 1. Presented By: Netra PrasadNeupane 17BPH080
- 2. ISOZYME • Isoenzymes orisozymes are mutiple forms of same enzyme that catalyse the same chemical reaction • Different chemical and physical properties.eg Electrophoretic mobility, Kinetic properties a, Amino acid sequenceand Amino acid composition • Property E.g.No1 Electrophoretic Isoenzymes of Lactate dehydrogenase have mobility different electrophoretic mobility • Heat stability Alkaline phosphatase isoenzymes are either heat labile or stable
- 8. Enzyme regulation can bechanged: 1. Enzyme production – synthesis or degradation 2. Compartmentation – different metabolic pathways occur in different cell compartments 3. Activation and inhibition – by activators or inhibitors, for example feed back inhibition by one of products of the reaction 4. Post-translational modification – for example by phosphorylation, methylation, glycosylation 5. Localization to a different environment – from a reducing (cytoplasm) to an oxidizing (periplasm) environment, of high pH to a low pH, or low salinity to high salinity, high to low energy charge
- 9. Cyclic phosphorylationand dephosphorylation is a common cellular mechanism for regulating protein activity In this example, the target protein R (orange) is inactive when phosphorylated and active when dephosphorylated; the opposite pattern occurs in some proteins. A linear representation of the conversion of chymotrypsinogen into chymotrypsin by the excision of two dipeptides These reactions yield three separate chains (A, B, and C), which are covalently linked by disulfide bonds (yellow) in the active enzyme
- 10. Allosteric regulationof aspartate transcarbamoylase (ATCase), the initial enzyme in synthesis of pyrimidines This enzyme comprises a pair of trimeric catalytic subunits (orange) connected by three pairs of dimeric regulatory subunits (green). Binding of cytidine triphosphate (CTP; the blue dot ) to the regulatory subunits causes a conformational transition from the active R state to the inactive T state. The more open conformation of the R state permits substrate binding. Thus an increase in the concentration of CTP, an end product in the pyrimidine pathway, shuts off ATCase, an example of feedback inhibition
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