Biosynthesis of sulfoquinovosyldiacylglycerol in higher plants: the incorporation of 35SO4 by intact chloroplasts.

Isolated spinach chloroplasts have been found to incorporate 35SO4 into the plant sulfolipid, sulfoquinovosyldiacylglycerol, at rates of up to 700 pmol mg chlorophyll-1 h-1. The reaction is light-dependent, requires that the chloroplasts be intact, and is slightly stimulated by ATP and UTP. UDP-galactose inhibits the formation of sulfoquinovosyldiacylglycerol, presumably by competing for the diacylglycerol pool. The rates of synthesis observed are sufficient to conclude that the chloroplast is autonomous with respect to the synthesis of sulfoquinovose, the headgroup moiety of sulfoquinovosyldiacylglycerol. No evidence could be obtained to support the concept that the proposed sulfoglycolytic pathway is the biosynthetic route for sulfoquinovose formation.