Michaelis-Menten constant definition

In a study of the highly purified alanine racemase of E. coli, Lambert and Neuhaus determined significant differences in the maximal velocities and the Michaelis-Menten constants of the substrates in the forward (L - dl) and reverse directions (d - dl) [37]. From these data the value calculated for Keq is 1.11 0.15. The time course of the reaction showed that in 10 min with L-alanine as substrate ca. 0.09 jumol of D-alanine were formed. With the same amount of enzyme (750 ng) and in the same time period, ca. 0.05 jamol of L-alanine were formed from D-alanine. Similar results have been reported for the same enzyme from S. faecalis and for proline racemases [37]. Thus, in these cases, there are definite kinetic differences, as expected for the existence of two diastereoisomers formed between enzyme and two substrate enantiomers. 

Magnetic moment, 153, 155, 160 Magnetic quantum number, 153 Magnetization, 160 Magnetogyric ratio, 153, 160 Main reaction, 237 Marcus equation, 227, 238, 314 Marcus plot, slope of, 227, 354 Marcus theory, applicability of, 358 reactivity-selectivity principle and, 375 Mass, reduced, 189, 294 Mass action law, 11, 60, 125, 428 Mass balance relationships, 19, 21, 34, 60, 64, 67, 89, 103, 140, 147 Maximum velocity, enzyme-catalyzed, 103 Mean, harmonic, 370 Mechanism classification of. 8 definition of, 3 study of, 6, 115 Medium effects, 385, 418, 420 physical theories of, 405 Meisenheimer eomplex, 129 Menschutkin reaction, 404, 407, 422 Mesomerism, 323 Method of residuals, 73 Michaelis constant, 103 Michaelis—Menten equation, 103 Microscopic reversibility, 125... 

Conditions where [S] are often known as the fccat conditions of catalysis. When [S] Km there is no free biocatalyst E at all, hence the first equilibrium effectively disappears and the measured rate constant of reaction, kp in Equation (8.107), becomes identified directly with the first order Michaelis-Menten term kcat according to Equations (8.1) and (8.9). In a similar way, AGo+in Equation (8.108) becomes identified directly with AG+p by definition. If both ES and ES+are bound equally more effectively by a uniform value AGp (Figure 8.55), then Ks and by implication K are reduced, but there is no change in fccat- If ES is bound to... 

The reciprocal form of the equation produced a straight line with intercept values on the Y axis of 1/Vmax and on the X axis of -1/Km (Figure 2). This advancement in analysis of the Michaelis-Menten equation allowed for a simplified way of analyzing the effect of compounds that altered the catalytic activity of enzyme systems. Changes in enzymatic activity were observed to result from changes in the substrate affinity or maximum velocity (Lineweaver Burk 1934) resulting in the definition of inhibitory equations based on their effects on the kinetic constants of the Michaelis-Menten equation. 

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