Phosphatidate phosphatase

To biosynthesize fats (triacylglycerols), the phosphate residue is again removed by hydrolysis (enzyme phosphatidate phosphatase 3.1.3.4). This produces diacylglycerols (DAG). 

Selected entries from Methods in Enzymology [vol, page(s)] Phosphatidate phosphatase from yeast, 197, 548 characterization and assay of phosphatidate phosphatase, 197, 553. 

Diacyl-sn-glycerol, formation of, PHOSPHATIDATE PHOSPHATASE PHOSPHOLIPASE C... 

PHOSPHATIDATE PHOSPHATASE PHOSPHATIDATE CYTIDYLYLTRANSFERASE PHOSPHATIDATE PHOSPHATASE Phosphatidolipase,... 

In many in vitro studies the acylation of the sn-3 position appears to be the rate-limiting step in TG synthesis. It has been suggested that the intracellular concentration of medium chain fatty acids may limit the final acylation reaction in TG synthesis (Dimmena and Emery 1981). Another theory is that the concentration of phosphatidate phosphatase, the enzyme that hydrolyzes the phosphate bond in phospha-tidic acid, yielding DG, may be the limiting factor (Moore and Christie 1978). The DG acyltransferase responsible for the final acylation of milk TG has been studied in mammary tissue from lactating rats (Lin et al. 1976). It was observed to be specific for the sn-1,2 DG, with very little activity observed with the sn-1,3 or sn-2,3 DG. It exhibited a broad specificity for acyl donors. The acyl-CoA specificity was not affected by the type of 1,2 DG acceptor offered, which implies that the type of fatty acid introduced into the glycerol backbone was not influenced by the specificity of subsequent acylation steps. However, the concentration of acyl donors will affect the final acylation. It was ob-... 

A second messenger, 1,2-diacylglycerol, can be formed from phosphatidylcholine (lecithin) by hydrolytic (Uni-substrate) reactions catalyzed by phospholipase C or by the combination of 3-sn-phosphatidate phosphatase and phospholipase D ... 

Suppose a cell is deficient in phosphatidate phosphatase, which catalyzes the formation of diacylglycerol from phosphatidate. What effects on lipid metabolism would you expect ... 

Glyceride and phospholipid metabolism Glycetol-3-phosphate dehydrogenase Phosphatidate phosphatase Ethanolamine phosphotransferase Choline phosphotransferase Ceramide choline phosphotransferase... 

Ion transport Adenosinetriphosphatase Adenosinetriphosphate pyrophosphatase Phosphatidate phosphatase... 

However, the acid phosphatase activity of rat iiver lysosomes has recently been resolved into at least two enzymes [531]. Acid phosphatase is used in subcellular fractionation studies as a marker enzyme for lysosomes. Both acid phosphatase [E.C. 3.1.3.2] and alkaline phosphatase [E.C. 3.1.3.1] activities should not be confused with other specific phosphatases with high specificity requirements for substrate, e.g. glucose-6-phos-phatase, fructose-l,6-diphosphatase, phosphatidate phosphatase. Several assay procedures are available, u.v. estimation can be achieved using phosphoenolpyruvate as a substrate and lactate dehydrogenase in an indicator reaction [539]. Colorimetric assays can be based upon the liberation of phenol from phenylphosphate [540], upon the Uberation of phosphate from sodium /3-glycerophosphate [541], upon the hydrolysis of sodium phenolphthalein phosphate [542], or upon the hydrolysis of p-nitrophenyl phosphate [543]. 

Fig. 2. Acylglycerols. Biosynthesis of triacylglycer-ols in liver and adipose tissue cells. EC 1.1.1.8 Glycerol-3-phosphate dehydrogenase (NAD "). EC 2.3.1.15 (j ycerol-3-phosphate acyltransferase. EC 2.3.1.20 Diacylglycerol acyltransferase. EC 2.3.1.51 1-AcylgIycerol-3-phosphate acyltransferase. EC 3.1.3.4 Phosphatidate phosphatase. EC 6.2.1.3 Long-chaln-fatty acid-CoA ligase.

Glycerophosphate acyltransferase, 1-acylglycerophosphate acyltransferase 2 phosphatidate phosphatase 3 diacylglycerol acyltransferase... 

At higher concentrations than 100 yM an inhibition of PA conversion into DG results. However at concentration of 10 yM a decrease in IPG labeling from C-glycerol takes place and an enhanced flow of radioactivity towards CPG, EPG and TG occurs. Thus two different mechanisms are needed to explain these observations. Both stimulatory and inhibitory actions on the phosphatidate phosphatase are suggested to account for the biphasic drug action as well as opposite effects on the conversion of PA in IPG take place (Table 3). 

The third dual effect was found when C-choline labeling was followed. The stimulation observed at early incubation times likely is brought about by a mechanism other than an inhibition of phosphatidate phosphatase (see below). The lowering in C-choline incorporation at later incubation times may involve diacylglycerol shortage or a direct action on the route of synthesis from choline. 

THE PURIFICATION AND CHARACTERISATION OF PHOSPHATIDATE PHOSPHATASE FROM AVOCADO... 

Ichihara, K., Murota, N. and Fujii, S. (1990) Intracellular translocation of phosphatidate phosphatase in maturing safflower seeds a possible mechanism of feedforward control of triacylglycerol synthesis by fatty acids, Biochim. Biophys. Acta 1043,227-234... 

Lin, Y-P. and Carman, G.M. (1989) Purification and characterisation of phosphatidate phosphatase from Saccharomyces cerevisiae, Journal of Biological Chemistry 264, 8641-8645... 

Kocsis, M.G., Weselake, R.J., Eng, J.A., Furukawastoffer, T.L. and Pomeroy, M.K. (1996) Phosphatidate phosphatase from developing seeds and microspore derived cultures of Brassica Napus, Phytochemistry 41, 353-363... 

Malherbe, A., Block, M.A., Douce, R. and Joyard, J. (1995) Solubilisation and biochemical properties of phosphatidate phosphatase from spinach chloroplast envelope membranes. Plant Physiol. Biochem. 33, 149-161... 

The Purification and Characterisation of Phosphatidate Phosphatase from Avocado. M. Pearce and A.R. Slabas. 

Figure 3.3 Enzyme systems associated with glycerolipid formation, (a) Glycerol kinase (EC 2.7.1.30) (b) glycerol-3-phosphate acyltransferase (EC 2.3.1.15) (GPAT) (c) 1-acyl-glycerol-3-phosphate acyltransferase (EC 2.3.1.51) (LPAAT) (d) phosphatidate phosphatase (EC 3.1.3.4) (e) diacylglycerol acyltransferase (EC 2.3.1.20) (DAGAT) (f) cholinephosphotransferase (EC 2.7.8.2) (CPT) (g) 1-acylglycerophosphocholine acyltransferase (EC 2.3.1.23).

Phosphatidate phosphatase (EC 3.1.3.4) associated with the production of DAG on enzymatic hydrolysis of PA is presumed to have little influence over the fatty acid composition of TAG (Hills and Murphy, 1991). 

Intestinal phosphatidate phosphatase. Biochim. biophys. Acta (Amst.) 56, 365 (1962). 

In higher plants, the lipolytic enzymes and their physiological functions are not well characterized [1]. iMost reports demonstrated that phospholipid catabolism in plants is achieved by the concerted actions of membrane-bound enzymes including phospholipase D, phosphatidate phosphatase, lipolytic acyl hydrolases and lipoxygenases [1,2]. With the exception of the phospholipase D, the literature on plant phospholipases is still very limited. We previously reported that tonoplast from Acer pseudoplatanus cells contains small amounts of phosphatidic acid and lysophospholipids, which were produced together with free fatty acids, particularly after addition of Ca " [31. These data suggested the possible involvement of phospholipase D and phospholipase A in the metabolism of vacuolar membrane lipids. The phospholipase activities were studied by following the hydrolysis of added sn-2-[14c]linoleyl-PC to tonoplast vesicles. Tonoplast was obtained by osmotic lysis of pure preparations of vacuoles isolated from protoplasts derived from Acer pseudoplatanus cells [4]. This present work demonstrated clearly the presence of phospholipase D and phospholipase Ai activities associated with the tonoplast of Acer, The phospholipase Ai showed an optimal activity at pH about 6-6.5, did not necessarily require divalent cations, but was stimulated by Mg- and particularly by Ca. This work presents the first evidence for the presence of phospholipases A in plant cells. 

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