ENZYME KINETICS Kinetic Properties of Enzymes and Derivation of Michaelis Menten equation (original) (raw)

Enzymes are extraordinary bio-catalyst. All the enzymes are protein except ribozymes. Enzyme increases the reaction rate of about 7 to 14 orders. They are also very specific for their particular substrate. During formation of enzyme substrate complex a small amount of free energy release that lower the activation energy of reaction. Ribozyme A ribozyme (from ribonucleic acid enzyme, also called RNA enzyme or catalytic RNA) is an RNA molecule that catalyzes a chemical reaction. Many natural ribozymes catalyze either their own cleavage or the cleavage of other RNAs, but they have also been found to catalyze the aminotransferase activity of the ribosome. Investigators studying the origin of life have produced ribozymes in the laboratory that are capable of catalyzing their own synthesis under very specific conditions, such as an RNA polymerase ribozyme. More work needs to be done in this area though, as the polymerase ribozyme does not have enough catalytic prowess: it is able to add up to 14 nucleotides to a primer template in 24 hours until it is decomposed by hydrolysis of the phosphodiester bonds Example: A recent test-tube study of prion folding suggests that an RNA may catalyze the pathological protein conformation in the manner of a chaperone enzyme.Some known ribozymes include RNase P, Group I and Group II introns, leadzyme, hairpin ribozyme, hammerhead ribozyme, hepatitis delta virus ribozyme, and tetrahymena ribozyme. Kinetics of enzymatic reaction starts with the substrate concentration [S] and initial velocity Vo. When substrate concentration is very low, initial velocity also low, if substrate concentration increases progressively but enzyme concentration is constant then Vo increases almost linearly with as increasing substrate concentration [S]. At very high substrate concentration Vo increases by smaller and smaller amounts and finally reach a plateau that is called maximum velocity i.e. Vmax Enzyme-substrate (ES) complex is the key to understanding the kinetic behaviors of enzymatic reaction that is proposed by Victor – Henri 1903. This idea expended and give a general theory of an enzymatic reaction by Leonor – Michaelis and Maud Menten in 1913. Fig. 1. shows the relationship between [S] and V0 for an enzymatic reaction. The hyperbolic shape of this curve can be expressed algebraically by the Michaelis-Menten equation. Derivation of Michaelis-Menten equation stars with two basic reaction involved in the formation and breakdown of ES. E + S ES 2 2 K K  E + P In equation , E = Enzyme. P = product, S = substrate, ES = Enzyme substrate complex, K1 = rate of constant of ES formation, K2 and K-1 are the rate of constant of ES break down. However K-2 is negligible and ignored. V0 is initial velocity determine from the break down of ES. V0 = K2 [ES]………………………………(2)

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