KEGG   ENZYME: 2.4.1.184Help
Entry
EC 2.4.1.184                Enzyme                                 

Name
galactolipid galactosyltransferase;
galactolipid-galactolipid galactosyltransferase;
galactolipid:galactolipid galactosyltransferase;
interlipid galactosyltransferase;
GGGT;
DGDG synthase (ambiguous);
digalactosyldiacylglycerol synthase (ambiguous);
3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol:mono-3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol beta-D-galactosyltransferase;
3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol:3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol beta-D-galactosyltransferase;
SFR2 (gene name)
Class
Transferases;
Glycosyltransferases;
Hexosyltransferases
BRITE hierarchy
Sysname
1,2-diacyl-3-O-(beta-D-galactosyl)-sn-glycerol:1,2-diacyl-3-O-(beta-D-galactosyl)-sn-glycerol beta-D-galactosyltransferase
Reaction(IUBMB)
2 a 1,2-diacyl-3-O-(beta-D-galactosyl)-sn-glycerol = a 1,2-diacyl-3-O-[beta-D-galactosyl-(1->6)-beta-D-galactosyl]-sn-glycerol + a 1,2-diacyl-sn-glycerol [RN:R04472]
Reaction(KEGG)
Substrate
1,2-diacyl-3-O-(beta-D-galactosyl)-sn-glycerol [CPD:C03692]
Product
1,2-diacyl-3-O-[beta-D-galactosyl-(1->6)-beta-D-galactosyl]-sn-glycerol [CPD:C20991];
1,2-diacyl-sn-glycerol [CPD:C00641]
Comment
The enzyme converts monogalactosyldiacylglycerol to digalactosyldiacylglycerol, trigalactosyldiacylglycerol and tetragalactosyldiacylglycerol. All residues are connected by beta linkages. The activity is localized to chloroplast envelope membranes, but it does not contribute to net galactolipid synthesis in plants, which is performed by EC 2.4.1.46, monogalactosyldiacylglycerol synthase, and EC 2.4.1.241, digalactosyldiacylglycerol synthase. Note that the beta,beta-digalactosyldiacylglycerol formed by this enzyme is different from the more common alpha,beta-digalactosyldiacylglycerol formed by EC 2.4.1.241. The enzyme provides an important mechanism for the stabilization of the chloroplast membranes during freezing and drought stress.
History
EC 2.4.1.184 created 1990, modified 2005, modified 2015
Pathway
Glycerolipid metabolism
Reference
1
  Authors
Dorne, A.-J., Block, M.A., Joyard, J. and Douce, R.
  Title
The galactolipid-galactolipid galactosyltransferase is located on the outer surface of the outer-membrane of the chloroplast envelope.
  Journal
FEBS Lett. 145 (1982) 30-34.
Reference
2
  Authors
Heemskerk, J.W.M., Wintermans, J.F.G.M., Joyard, J., Block, M.A., Dorne, A.-J. and Douce, R.
  Title
Localization of galactolipid:galactolipid galactosyltransferase and acyltransferase in outer envelope membrane of spinach chloroplasts.
  Journal
Biochim. Biophys. Acta 877 (1986) 281-289.
Reference
3
  Authors
Heemskerk, J.W.M., Jacobs, F.H.H. and Wintermans, J.F.G.M.
  Title
UDPgalactose-independent synthesis of monogalactosyldiacylglycerol. An enzymatic activity of the spinach chloroplast envelope.
  Journal
Biochim. Biophys. Acta 961 (1988) 38-47.
Reference
4  [PMID:14600212]
  Authors
Kelly AA, Froehlich JE, Dormann P.
  Title
Disruption of the two digalactosyldiacylglycerol synthase genes DGD1 and DGD2 in Arabidopsis reveals the existence of an additional enzyme of galactolipid synthesis.
  Journal
Plant. Cell. 15 (2003) 2694-706.
Reference
5  [PMID:15590685]
  Authors
Benning C, Ohta H.
  Title
Three enzyme systems for galactoglycerolipid biosynthesis are coordinately regulated in plants.
  Journal
J. Biol. Chem. 280 (2005) 2397-400.
Reference
6  [PMID:18466306]
  Authors
Fourrier N, Bedard J, Lopez-Juez E, Barbrook A, Bowyer J, Jarvis P, Warren G, Thorlby G
  Title
A role for SENSITIVE TO FREEZING2 in protecting chloroplasts against freeze-induced damage in Arabidopsis.
  Journal
Plant. J. 55 (2008) 734-45.
  Sequence
[ath:AT3G06510]
Reference
7  [PMID:20798281]
  Authors
Moellering ER, Muthan B, Benning C
  Title
Freezing tolerance in plants requires lipid remodeling at the outer chloroplast membrane.
  Journal
Science. 330 (2010) 226-8.
Other DBs
ExplorEnz - The Enzyme Database: 
IUBMB Enzyme Nomenclature: 
ExPASy - ENZYME nomenclature database: 
BRENDA, the Enzyme Database: 
CAS: 
66676-74-2

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