Please help 10 (1. O (I, Pyruvate kinases are regulated by fructose diphosphate

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10 (1. O (I, Pyruvate kinases are regulated by fructose diphosphate (FDP), by AMP and by ribose-5-P in Escherichia coli Using a sketch of the glycolytic pathways, explain the significance or these regulators. likely Valentini et al. (2000) published a structure of E, coli FDP-activated pyruvate kinase, said to be in t I state. Explain what this means and what reasons suggest the enzyme is in the T state. The structu of the rabbit muscle enzyme published later was said to be in the R state (explain)

Explanation / Answer

Pyruvate kinase (PK) catalyzes the final irreversible step in glycolysis, that is the second substrate level phosphorylation reaction (forms 2ATP) by converting Phosphoenol pyruvate into Pyruvate. The enzyme therefore represents an important control point and is allosterically activated by fructose-1,6-bisphosphate (FBP) and by high AMP level.

FBP activation induce conformational changes or allosteric transition from the inactive (T) state to the active (R) state of the enzyme pyruvate kinase.

b) Behaviour of allosteric enzymes -

It is explained by Concerted model that states that -

The binding of the first molecule of the substrate triggers the binding of the second substrate molecule to the other subunit, termed as cooperative binding. In the absence of substrate, the enzyme exists in T form, in equilibrium with small amount of R form. The presence of substrate shifts the equilibrium to produce more R forms.

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