FIG 4.

Activating effect of ionic and osmotic compounds on the enzyme activity of SPS₇₉₄₂. (a, c, and d) Fructose-6-phosphate and UDP-glucose were used as substrates (2 mM each) to determine the bifunctional activity of SPS₇₉₄₂. (b) Sucrose-6-phosphate (2 mM) was used to examine the SPP activity of SPS₇₉₄₂. Different concentrations of NaCl, KCl, NaNO₃, NH₄Cl, sorbitol, and mannitol were included in reaction mixtures, as indicated. The data are presented as means from independent replicates (n = 3 in panels a and d; n = 4 in panels b and c) with the standard deviations; the data of KCl and NH₄Cl in panel d are presented as means from two independent replicates with the standard deviations. In each panel, all obtained values at different concentrations were normalized by comparing them to the value at 0 mM.