Fig. 2 in How is the activity of shikimate dehydrogenase from the root of Petroselinum crispum (parsley) regulated and which side reactions are catalyzed?

Fig. 2. Product inhibition analysis for the determination of the mechanism of bisubstrate reaction in the direction from SA to DHS (A-F) and in the direction from DHS to SA (G-J). Experimental data are fitted with calculated values determined by non-linear regression using equations charactering competitive and non-competitive inhibition, respectively. SDH products DHS (A,B,C) and NADPH (D,E,F) served as competitive (B,C,D,F) and non-competitive (A,E) inhibitors. The saturating (C,F) and subsaturating (A,B,D,E) concentrations of SA and NADP were 20 mM and 2 mM, and 0.3 mM and 0.5 mM, respectively. Saturating concentrations of NADP and variable concentrations of SA caused no inhibition (N.I.) of NADPH and saturating concentrations of SA and variable concentrations of NADP caused N.I. of DHS (data not shown). SDH products SA (G,H) and NADP (I,J) served as competitive (G,I) and non-competitive (H,J) inhibitors at 0.75 mM (subsaturating concentration) DHS (G,I) and 0.2 mM (subsaturating concentration) NADPH (H,J) as a second substrate. Ki indicates inhibition constants in mM. NC - noncompetitive and C - competitive inhibition. Measurements were performed in doublets (S.D. are shown) and at least 2-4 times (enzyme preparations from different isolations).