Talk:Structural Biochemistry/Enzyme/Michaelis and Menten Equation

The statements in this wiki book about KM are incorrect: "It can also be thought of as a measure of how well a substrate complexes with a given enzyme, otherwise known as its binding affinity. An equation with a low Km value indicates a large binding affinity, as the reaction will approach Vmax more rapidly. An equation with a high Km indicates that the enzyme does not bind as efficiently with the substrate, and Vmax will only be reached if the substrate concentration is high enough to saturate the enzyme." This statement assumes a rapid equilibrium model for substrate bindidng the substrate and discounts the effect of the forward reaction, therefore equating KM with KD (Dissociation constant). Although this treatment was originally used by Michaelis and Menten, it is likely not valid for most enzymes, in which the rate of the forward reaction is significant compared to the substrate-enzyme dissociation rate and may even be orders of magnitude greater in some cases (KM = (k-1 + k2)/k+1 = KD + k2/k1 in its simplest form). This is a fundamental misconception in enzymology,which is propagated in this web book and many biochemistry and biology text books.

Furthermore, kcat, is written with a lower case "k", rather than the upper case "K" used in wiki text book. Again, this is significant, since students and others will propagate this error in the literature.