Lec 11[1] - Lec 11 We talked about basics of Michaelis...

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Lec 11 We talked about basics of Michaelis Menten ---dependence of enzymatically catalized reaction on substrate concentration is hyperbolic, with two parameters : 1) Vmax--- maximum velocity, with particular enzyme concentration 2) substrate concentration when ½ of Vmax which is Km. Km is substrate concentration, it is NOT velocity, it is substrate concentration where ½ Vmax. Hyperbola approaching Vmax, ½ Vmax substrate concentration equals Km. One can relate Km to the kinetic K. The equilibrium constant for binding of substrate to form reversible complex will be k-1/k1. Km is the sum of 2 dissociation rate constants (dissociation back to free enzyme and substrate and dissociation constant to the product divided by the association constant). Km is independent of the delta G between substrate and product, but is related to the Activation energy change , Km is sometimes approximation of equilibrium between substrate and transition state. Free energy of activation is expressed with Kp, one can estimate uncatalyzed rate of reaction . And drop of activation energy, increase of rate constant is measure of how good catalyzed is. The lineweaver Burk transformation: x intercept is 1/Km (inverse of substrate concentration), y intercept is 1/Vmax. The slope of this line Km/Vmax. When increasing Vmax , (is measure of Vmax=Kcat times the total enzyme concentration) puts the value of 1/Vmax lower and lower . Km is the tendency of substrate enzyme to dissociate back to free , the lower Km (look at absolute terms) the higher the affinity of the enzyme for the substrate, and higher the value of x intercept. Not all enzymes deal with transformation of single substrate to single product. Diagram, implicit mechanism, reaction starts with binding of A, and when A is bound, B can bind as well--- obligate binding order. Also there is possible of AB and BA binding which is random binding order. When random order , there are two separated sites for 2 substrates and sites do not talk to each other , substrate just bind with their own affinities , the binding does not affect affinity of the other one --- non cooperative binding. When handling the two molecules of the same substrate, and substrate binding sites do not talk to each other, to find Km, you will get the plots and one sees apparent Km is unaffected
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This note was uploaded on 01/30/2010 for the course BIO 351 taught by Professor Hoffmann,j during the Fall '08 term at SUNY Stony Brook.

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Lec 11[1] - Lec 11 We talked about basics of Michaelis...

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