Re-evaluation of plant sulpholipid labelling from UDP-[14C]glucose in pea chloroplasts

Abstract

The sulphoquinovosyldiacylglycerol (sulpholipid) zone obtained by TLC of pea chloroplast lipids yields, on hydrolysis, not only sulphoquinovose but also galactose and glucose. Following incorporation from UDP-["%C]glucose, the percentages of the total radioactivity in these three sugars were typically 1, 5 and 85 %, respectively. The occurrence of the glucolipid causes

A Chloroplastic UDP-Glucose Pyrophosphorylase from Arabidopsis Is the Committed Enzyme for the First Step of Sulfolipid Biosynthesis

“…UDP-Glc for SQDG biosynthesis has also been speculated to be of cytosolic origin, and certain proteins have been proposed as the candidate transporters of UDP-Glc for SQDG biosynthesis (Knappe et al, 2003). However, a feeding experiment in which radiolabeled UDP-Glc was applied to isolated chloroplasts of the pea revealed that radioactivity was not efficiently incorporated into the sulfoquinovose moiety (Roy and Harwood, 1999), raising the question of how UDP-Glc is transported to the chloroplasts. This study revealed that UDPGlc for SQDG biosynthesis is generated in the chloroplasts by the UGP3 protein, not incorporated from extrachloroplastic space ( Figure 9).…”