The used of the efficiency function for comparing catalytic competence

CECCARELLI, E. A.; CARRILLO, N; ROVERI, O. A

Villa Carlos Paz, Córdoba

Congreso; Reunión Anual de la Sociedad Argentina de investigación en Bioquímica y Biología Molecular (SAIB); 2008

Sociedad Argentina de investigación en Bioquímica y Biología Molecular (SAIB)

The use of k /K to compare the catalytic competence of enzyme cat Mvariants is inappropriate, since the ratio between the reactionvelocities depends on [S] even when both variants have equal k /K cat Mif they have different K values (Eisenthal, R. et al. (2007) Trends MBiotechnol 25, 247).In chemical catalysis, the efficiency function (Ef) is defined(Albery, W.J., Knowles, J.R. (1976) Biochemistry 15, 5631) as theratio between the rate of the catalyzed reaction and the maximumtheoretical rate, which is limited by diffusion of substrates to theactive site. We derived a formalism by applying the steady-stateapproximation, and proposed its use for comparing the competenceof enzyme-catalyzed reactions (Ceccarelli, E.A. et al. (2008) TrendsBiotechnol 25, 119). Ef permits: i) a straightforward interpretationof changes in catalytic competence in terms of “efficiency” for thebiotechnological practice; and ii) the evaluation of how far variousengineered enzymes have approached the “catalytic perfection”,viz. they are beyond diffusion control.Ef provides a direct, easy and useful tool to make predictions on theconditions under which an enzyme variant could be efficientlyemployed. If physiological [S] are known, it can also be used topredict if expression of a mutated enzyme in a transgenic organismwill improve the efficiency of conversion of a desired substrate.