1,2-Dioleoyl-sn-glycerol

AtDGK2, a novel diacylglycerol kinase from Arabidopsis thaliana, phosphorylates 1-stearoyl-2-arachidonoyl-sn-glycerol and 1,2-dioleoyl-sn-glycerol and exhibits cold-inducible gene expression.[Pubmed:14665624]

J Biol Chem. 2004 Feb 27;279(9):8230-41.

Diacylglycerol kinase (DGK) phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Both DAG and PA are implicated in signal transduction pathways. DGKs have been widely studied in animals, but their analysis in plants is fragmentary. Here, we report the cloning and biochemical characterization of AtDGK2, encoding DGK from Arabidopsis thaliana. AtDGK2 has a predicted molecular mass of 79.4 kDa and, like AtDGK1 previously reported, harbors two copies of a phorbol ester/DAG-binding domain in its N-terminal region. AtDGK2 belongs to a family of seven DGK genes in A. thaliana. AtDGK3 to AtDGK7 encode approximately 55-kDa DGKs that lack a typical phorbol ester/DAG-binding domain. Phylogenetically, plant DGKs fall into three clusters. Members of all three clusters are widely expressed in vascular plants. Recombinant AtDGK2 was expressed in Escherichia coli and biochemically characterized. The enzyme phosphorylated 1,2-Dioleoyl-sn-glycerol to yield PA, exhibiting Michaelis-Menten type kinetics. Estimated K(m) and V(max) values were 125 microm for DAG and 0.25 pmol of PA min(-1) microg(-1), respectively. The enzyme was maximally active at pH 7.2. Its activity was Mg(2+)-dependent and affected by the presence of detergents, salts, and the DGK inhibitor R59022, but not by Ca(2+). AtDGK2 exhibited substrate preference for unsaturated DAG analogues (i.e. 1-stearoyl-2-arachidonoyl-sn-glycerol and 1,2-Dioleoyl-sn-glycerol). The AtDGK2 gene is expressed in various tissues of the Arabidopsis plant, including leaves, roots, and flowers, as shown by Northern blot analysis and promoter-reporter gene fusions. We found that AtDGK2 is induced by exposure to low temperature (4 degrees C), pointing to a role in cold signal transduction.

Microsomal diacylglycerol acyltransferase in rat parotid and submandibular glands: acylation of 1,2-dioleoyl-sn-glycerol dispersed with phospholipids.[Pubmed:8811837]

Int J Biochem Cell Biol. 1996 Aug;28(8):895-903.

In order to investigate microsomal diacylglycerol acyltransferase activity, ethanol or several detergents have been used as a dispersing agent for water-insoluble substrates. However, ethanol acyltransferase interferes with the activity of this enzyme, and detergents inhibit it. We examined the properties of microsomal diacylglycerol acyltransferase in rat salivary glands without detergents or organic solvents. 1,2-Dioleoyl-sn-glycerol (1,2-diolein) was dispersed by sonication. The activity was measured as the formation rate of [14C]triglyceride using [1-14C]palmitoyl-CoA as an acyl-donor. The reaction was dependent on the microsomal protein and 1,2-diolein at least up to 145 micrograms/ml and 3.6 mM, respectively. The specific activities were 3.91 +/- 0.57 and 3.80 +/- 0.77 nmol/min per mg protein (SEM, n = 4) in the parotid and submandibular glands, respectively. They were 12- to 20-fold higher than the activities in liver, brain and spleen, and two orders of magnitude higher than that assayed with microsomal endogenous diacylglycerol. Adding tissue phospholipids to 1,2-diolein suspension reduced the concentration of 1,2-diolein required for the maximal velocity. A similar, but reduced, effect was induced by egg yolk phosphatidylcholine in place of the tissue phospholipids. The level of activity was recovered by adding another phospholipid class to the phosphatidylcholine. The results suggested that the physical condition of the substrate diacylglycerol affects diacylglycerol acyltransferase activity in rat salivary gland microsomes.