Feeding experiments with free d-G1cA showed that plant cells rapidly incorporate the sugar into pectin (459). Free GlcA, likely released from wall polysaccharides, can be activated to UDP-GlcA, by-passing the need for flux of the sugar from the inositol oxidation pathway. Membrane and soluble protein preparations extracted from a 4-day-old etiolated seedlings of mung bean consist of a kinase activity that specifically phosphorylates GlcA in the presence of ATP and Mg2+ to GlcA-1-P. L-Ara and D-Gal are also substrates for this crude kinase preparation. However, GalA is not a substrate for this activity (411). The GlcA-1-P kinase has not been purified and the gene is not yet known. Work in our laboratory (Bar-Peled, 2005) (414) and by Schnurr and coworkers (415) demonstrated that Sloppy (At5g52560) is the true GlcA-1-P pyrophosphorylase and readily converts UTP and GlcA-1-P into UDP-GlcA.