Estimativa dos parâmetros cinéticos Km e Vmáx por uma aproximação gráfico-matemática
Palavras-chave:
absorção de fósforo, cinética de michaelis-menten, parâmetros cinéticos, velocidade de absorção, concentração de fósforoResumo
A simple mathematical approach is proposed for calculating the kinetic parameters of Vmax, the maximum rate of influx, and Km, the Michaelis constant. The depletion of a nutrient quantity (umole) in solution is graphically represented as a function of time, and two regression equations are determined: one linear for the maximum slope region, and the other curvilinear, for the curvilinear region. The negative value of the slope of the linear regression equation divided by root mass represents Vmax. By setting equal the first derivative of the curvilinear regression equation with half the slope of the linear regression equation, a time is calculated. This value, introduced in the curvilinear regression equation, permits the estimation of the quantity of nutrient which, when divided by the solution volume, expresses Km.
Referências
CLAASSEN, N. & BARBER, S.A. A method for characterizing the relation between nutrient concentration and flux into roots of intact plants. Plant Physiol. 54:564-568. 1974.
EPSTEIN, E. Nutrição mineral das plantas: principios e perspectivas. São Paulo, Ed. dg Universidade de São Paulo, 1975. 433 p. & . HOFSTEE, B.H.J. On the evaluation of constants Vm and Km in enzyme reactions. Science 116:329-333. 1952.
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NELSON, R.A. & ANDERSON, R.L. Partitioning of soil testerop response probability. In: PECK, T.R. (ed.). Soil testing: correlating and interpreting the analytical results. Madison, ASA, CSSA, SSSA, 1977. 19-38 (ASA Special Publication Number 29).
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