Making sense of the kinetics of reactions of unstable modifiers with enzymes
1992; Portland Press; Volume: 287; Issue: 1 Linguagem: Inglês
10.1042/bj2870334
ISSN1470-8728
Autores Tópico(s)Microbial Metabolic Engineering and Bioproduction
ResumoBJ Letters sound), eqn. (11) of Topham (1990) is valid, since, although [X] is not > [E]O during the whole course ofthe reaction, the condition (5) is fulfilled.Fig. 1(b) shows that if the condition (6) (and the remaining assumptions of Topham), but not condition (5), is satisfied, then eqn.(11) of Topham (1990) fails.The numerical integration to obtain the simulated curves in Fig. 1 was carried out by the use of the predictor-corrector algorithm of Adams-Moulton, starting with the fourth order Runge-Kutta method (Gerald, 1978).Before plotting eqn. (11)of Topham (1990), we corrected the mistake: eik't instead of e-ct.For the acquisition of the points necessary to plot this equation, we elaborated a computer program using the BASIC language.This program is available to interested readers on request.It allows the choice of the number of terms in the infinite series in the kinetic equations.We progressively increased this number from 1 and, in all cases, the difference between the successive results vanished after less than 20 steps.For the plots of eqn. (1 1)of Topham (1990) in Fig. 1, we employed 20 terms.The algorithm for the numerical integration and the program elaborated by us were implemented and compiled in TurboBASIC 1.0 on an INVES PC-640A computer (IBM AT-compatible) with an Intel 80287 arithmetic coprocessor.The unnecessary assumption (6) probably led Topham (1990) to propose a kinetic data analysis, which is based on the first instants of the reaction (at which this assumption is fulfilled because the modifier has not yet decayed appreciably), although his equations are valid in the entire time range.Since for short reaction times, the exponential terms cannot be neglected, that approach suffers from both mathematical and experimental difficulties.
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