In enzymology, a galactolipid galactosyltransferase is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that catalyzes

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 the chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

2 3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol 3-[alpha-D-galactosyl-(1->6)-beta-D-galactosyl]-1,2-diacyl-sn- glycerol + 1,2-diacyl-sn-glycerol

Hence, this enzyme has one substrate

Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...

, 3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol, but 3 products

Product (chemistry)

Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...

: 3-[alpha-D-galactosyl-(1->6)-beta-D-galactosyl]-1,2-diacyl-sn-, glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, and 1,2-diacyl-sn-glycerol.

This enzyme belongs to the family of glycosyltransferase

Glycosyltransferase

Glycosyltransferases are enzymes that act as a catalyst for the transfer of a monosaccharide unit from an activated nucleotide sugar to a glycosyl acceptor molecule, usually an alcohol....

s, specifically the hexosyltransferases. The systematic name of this enzyme class is 3-(beta-D-galactosyl)-1,2-diacyl-sn-glycerol:mono-3-(beta-D-galactos yl)-1,2-diacyl-sn-glycerol beta-D-galactosyltransferase. Other names in common use include galactolipid-galactolipid galactosyltransferase, galactolipid:galactolipid galactosyltransferase, interlipid galactosyltransferase, GGGT, DGDG synthase (ambiguous), and digalactosyldiacylglycerol synthase (ambiguous). This enzyme participates in glycerolipid metabolism.