Ping-Pong mechanisms determination

One less kinetic parameter can be obtained from an analysis of the data for a ping-pong mechanism than can be obtained for ordered reactions. Nevertheless, in Eq. 9-47, twelve rate constants are indicated. At least this many steps must be considered to describe the behavior of the enzyme. Not all of these constants can be determined from a study of steady-state kinetics, but they may be obtained in other ways. 

The equihbrium constant may be determined independently of the rate measurements. For the ping-pong mechanism of Scheme 5 the equilibrium constant is ... 

Experimental design for the determination of kinetic parameters in ping-pong mechanism is analogous to the previously described for sequential mechanisms, so that Vap and Kap at different values of b are determined as the Y and X-axis intercepts... 

Determination of the Order of Addition of Reactants in Ter Ter Ping Pong Mechanisms... 

One of the most useful appKcations of isotope exchange studies comes in determining the order of addition of substrates in trisubstrate Ping Pong mechanisms. The best way to understand this problem is in relation to a specific example. Consider, for example, the reaction catalyzed by a large number of synthetases (Walsh, 1998) ... 

The steady-state derivation of the ping pong Bi Bi mechanism provides the following determinants for each of the enzyme forms ... 

The corresponding kinetic equation for Ping Pong Bi-Bi mechanism with competitive alcohol inhibition was used to fit the experimental data, determining the kinetic parameters by the following expression ... 

Steady-state kinetics have been used to determine the kinetic mechanisms of many of these enzymes. The questions that have been primarily addressed are the sequence of steps that occur in substrate binding prior and subsequent to the catalytic reaction and the potential formation of covalent enzyme intermediates. Classical interpretation of kinetic analyses has been the determination of the relevant reactions occurring via a random or an ordered sequential reaction, or if the reaction is a double-displacement or Ping-Pong reaction. In the former case, phosphoryl transfer occurs in the ternary complex that contains enzyme, phosphoryl donor, and phosphoryl acceptor. In the latter case, enzyme reacts with... 

There are various reports in the literature concerning kinetic studies of the Upase-catalyzed hydrolysis or synthesis of esters in microemulsions [8,9,49,83,84]. A simple MichaeUs-Menten kinetic model was proposed for the hydrolysis of triglycerides [85,86], while the esterifications of aliphatic alcohols with fatty acids follow a ping-pong bi-bi mechanism [87]. According to this mechanism the lipase reacts with the fatty acid to form a noncovalent enzyme-fatty acid complex, which is then transformed to an acyl-enzyme intermediate, while water, the first product, is released this is followed by a nucleophile attack (by the alcoholic substrate) to form another binary complex that finally yields the ester and the free enzyme. The kinetic parameters and determined in these studies represent apparent... 

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