Fig. 5. Effects of varying glutamine (Gln) concentration on carbamoyl phosphate synthetase III (CPSase III) activity in Clarias gariepinus larval extracts (313h post-fertilization) with or without N-acetyl-L-glutamate (AGA) present in the reaction mixture. The enzyme was obtained from gel chromatography (Fig.4, whole larvae) by pooling fractions from the second peak having more than 60% of maximum peak activity (protein concentration 0.59mgml^-1). Assays were conducted using standard conditions as described in the text, except as noted. The inset is a reciprocal plot of activity (V) versus substrate concentration. Because of the high dependence on AGA of this CPSase III, activity was too low and variable to estimate K_m in the absence of the effector. CP, carbamoyl phosphate.