Control Function of Hexosemonophosphate Isomerase and Phosphoglucomutase in Starch Synthesis of Leaves

Abstract

Within biochemical reaction sequences the overall reaction rate is a function not only of the thermodynamic driving force of the chemical reaction, but also a function of the amount of catalysts and the degree of substrate saturation of the catalysts involved in the reactions. Thus, every single enzyme within the sequence may contribute to the rate limitation imposed on the reaction, i.e. may exert control function; the values which describe this control function vary between 0 (no control function) and 1 (solely rate controlling). The sum of the control values of all enzymes involved in the considered reaction sequence is 1 (1). It is rather difficult to describe the control function of individual photosynthetic reactions in vivo and in vitro by numerical values. Control functions vary with changes in environmental parameters of photosynthesis.