1. UPD-Galactose-Independent Synthesis of Mono-Galactosyldiacylglycerol (MGDG). An Enzymatic Activity of the Spinach Chloroplast Envelope
- Author
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Johan W. M. Heemskerk, Frans H. H. Jacobs, and Jef F. G. M. Wintermans
- Subjects
Chloroplast ,Galactosyltransferase ,Tricine ,chemistry.chemical_compound ,Galactolipid ,chemistry ,Biochemistry ,Galactolipid galactosyltransferase ,Spinach ,Biology ,biology.organism_classification ,Chloroplast membrane ,Diacylglycerol kinase - Abstract
Various authors have noted that isolated chloroplasts, incubated under appropriate conditions, can synthesize small amounts of monogalactosyldiacylglycerol (MGDG) in the absence of UDPgalactose, either from labeled glycerol 3-phosphate [1] or from labeled acetate [2]. Van Besouw and Wintermans [3] tried to explain this phenomenon by a mechanism involving UDPgalactose:diacylglycerol galactosyltransferase (UDGT). In this paper we present evidence that UDPgalactose-independent MGDG synthesis is an enzymatic activity of the chloroplast envelope and that galactolipid:galactolipid galactosyltransferase (GGGT) is involved in the synthesis. Thus, GGGT catalyzes the reversible reaction of Eq.(1), permitted by an expected, low reaction enthalphy: $$\text {DGDG}\;\;+\;\; \text {diacylglycerol}\;\; \;\; \text {MGDG}\;\;+\;\; \text {MGDG}$$ (1) .
- Published
- 1989
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