Fig. 6.

An allosteric effect of G6P on the activity of recombinant SPSs and authentic SPS from plant leaves. Activity of Full (Sf9), HisΔN3, and HisΔN4 was measured in the assay mixture containing 20 mM UDP-G and 5, 10 or 20mM F6P. Effect of allosteric activator G6P was examined by the addition of increasing concentrations from 0 to 8 mM. As a control for the allosteric activation of SPS by G6P, a crude SPS fraction prepared from maize leaves was also assayed side by side. Reaction rate was determined as in Fig. 5A.