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At least 19 recordsLinked to original sources
PubMed1974

Degradation of monogalactosyl diglyceride and digalactosyl diglyceride by sheep pancreatic enzymes.

1. Saline extract of sheep pancreas acetone-dried powder was shown to catalyse acyl ester hydrolysis of spinach leaf galactosyl diglycerides and also galactosylglucosyl diglyceride of Lactobacillus casei. 2. Sodium deoxycholate stimulated the enzyme activity. Ca(2+) had no effect on the hydrolysis of monogalactosyl diglyceride, but it enhanced that of digalactosyl diglyceride. When added together, there was considerably less activity with both the substrates. 3. Optimal hydrolysis was observed at pH7.2. 4. The initial point of hydrolysis was at position-1, leading to the formation of monogalactosyl monoglyceride and digalactosyl monoglyceride. Further hydrolysis to the corresponding galactosylglycerols and later to galactose and glycerol was also observed, indicating the presence of alpha- and beta-galactosidases in the enzyme preparation. 5. Formation of monogalactosyl diglyceride from digalactosyl diglyceride by the action of alpha-galactosidase was noted. 6. Monogalactosyl diglyceride was also hydrolysed by beta-galactosidase to a limited extent, giving rise to diacylglycerol and galactose. 7. Attempts at purification of monogalactosyl diglyceride acyl hydrolase by using protamine sulphate treatment, Sephadex G-100 filtration and DEAE-cellulose chromatography gave a partially purified enzyme which showed 9- and 81-fold higher specific activity towards monogalactosyl diglyceride and digalactosyl diglyceride respectively. This still showed acyl ester hydrolysis activity towards methyl oleate, phosphatidylcholine and triacylglycerol. 8. When sheep, rat and guinea-pig tissues were compared, guinea-pig tissues showed the highest activity towards both monogalactosyl diglyceride and digalactosyl diglyceride. In all the species pancreas showed higher activity than intestine.

Animals↗
PubMed1979

Diglyceride kinase mutants of Escherichia coli: inner membrane association of 1,2-diglyceride and its relation to synthesis of membrane-derived oligosaccharides.

Mutants of Escherichia coli defective in diglyceride kinase contain 10 to 20 times more sn-1,2-diglyceride than normal cells. This material constitutes about 8% of the total lipid in such strains. We now report that this excess diglyceride is recovered in the particulate fraction, primarily in association with the inner, cytoplasmic membrane. The diglyceride kinase of wild-type cells was recovered in the same inner membrane fractions. The conditions employed for the preparation of the membranes did not appear to cause significant redistribution of lipids and proteins. The biochemical reactions leading to the formation of diglyceride in E. coli are not known. To determine whether diglyceride formation requires concurrent synthesis of the membrane-derived oligosaccharides (H. Schulman and E. P. Kennedy, J. Biol. Chem. 252:4250-4255, 1977), we have constructed a double mutant defective in both the kinase (dgk) and phosphoglucose isomerase (pgi). When oligosaccharide synthesis was inhibited in this organism by growing the cells on amino acids as the sole carbon source, the diglyceride was no longer present in large amounts. When glucose was also added to the medium, the pgi mutation was bypassed, oligosaccharide synthesis resumed, and diglyceride again accumulated. These findings suggest that diglyceride may arise during the transfer of the sn-glycero-1-P moiety from phosphatidylglycerol (and possibly cardiolipin) to the oligosaccharides. In wild-type cells the kinase permits the cyclical reutilization of diglyceride molecules for phospholipid biosynthesis.

Diglycerides↗
PubMed1980

Indomethacin-induced accumulation of diglyceride in activated human platelets. The role of diglyceride lipase.

Human platelets incubated with thrombin and indomethacin (50 microgram/ml) exhibit an accumulation of diglyceride larger and more persistent than that observed for platelets incubated with thrombin alone. The accumulation appears to be due to the impaired metabolism of diglyceride by diglyceride lipase. In preparations of broken platelets, indomethacin leads to inhibition of diglyceride lipase. A similar inhibition can be achieved by the addition of soybean lipoxidase, and both inhibitions can be counteracted by reduced glutathione. Further, hydroperoxyeicosatetraenoic acid (100 microM) markedly depresses diglyceride lipase activity, whereas neither the hydroxy derivative nor eicosatetraenoic acid displays a comparable effect. Indomethacin at concentrations comparable to those impairing diglyceride lipase does not inhibit diglyceride kinase. This report constitutes the first evidence for the functioning of diglyceride lipase in normal stimulated platelets, and points to a possible role for fatty acid hydroperoxides in governing the activity of this enzyme.

Arachidonic Acids↗
PubMed2002

Comparison of non-diglyceride- and diglyceride-based assays for pancreatic lipase activity.

Pancreatic lipase is produced and stored in pancreatic acinar cells, and is normally secreted into the duct system. In disorders that cause pancreatic damage, pancreatic lipase enters the circulation, and serum lipase activity becomes useful in the diagnosis and evaluation of pancreatitis. During the last decade, many lipase assays have used the Imamura method, in which a series of enzymatic reactions utilizing a diglyceride substrate leads to the formation of a colorimetrically detected product. Historically, this method has been prone to significant interference from various substances, including glycerol itself. In the light of these limitations, we evaluated an automated enzymatic rate assay that uses a non-diglyceride-based, pancreatic lipase-specific substrate. Precision, linearity, and potential interference were assessed, and when compared to the Imamura method, the non-diglyceride-based assay exhibited a slope of 0.475, y-intercept of 15.89, r-value of 0.9516, and S(y,x) of 12.96. Similar results were also observed when the two assays were compared using samples with markedly elevated creatinine levels. Between-day coefficients of variance (CVs) ranged from 5.0% to 5.5%, which compared well with the diglyceride-based method, and linearity spanned a range of 3-156 U/L. Evaluation of over 2,000 patient results collected during a 6-month period suggested that the manufacturer's upper reference limit of 51 U/L may be too conservative. No significant interference was identified with bilirubin, triglyceride, or glycerol itself, and significant interference from hemoglobin was observed only at concentrations of 116 mg/dL or greater. As a result, the non-diglyceride-based method provides an acceptable alternative for the routine laboratory measurement of lipase activity.

Clinical Laboratory Techniques↗
PubMed1991

Diglyceride Kinase Activity in Cell Extracts of Rhizobium meliloti: Evidence for a Diglyceride Cycle during Cyclic beta-1,2-Glucan Biosynthesis.

In this article, we provide evidence for the presence of diglyceride kinase activity in cell extracts of Rhizobium meliloti 1021. Characterization of the rhizobial enzyme revealed that it shares many properties with the diglyceride kinase of Escherichia coli. A possible role for this enzyme during cyclic beta-1,2-glucan biosynthesis is discussed.

Journal Article↗
PubMed2001

Determination of ceramides and diglycerides by the diglyceride kinase assay.

This review will discuss the utilization of the diglyceride (DG) kinase assay as an analytical method that allows the simultaneous quantitation of DG and ceramide from cell and tissue samples. This enzymatic approach is sensitive, quantitative, and linear over a broad range (20 pmol to 20-25 nmol) for both classes of lipids. It is also practical in that it can be applied to crude lipid extracts and used to process many samples (up to 100) concurrently. However, it has become apparent that this assay has not been conducted optimally, primarily as a result of lack of adherence to its basic principles. The principles illustrated here are also useful to all enzymatic quantitative methods.

Animals↗
PubMed1983

Appearance of monoglyceride and triglyceride in the cell envelope of Escherichia coli mutants defective in diglyceride kinase.

Diglyceride kinase mutants of Escherichia coli contain about 50- to 100-fold more 1,2-diglyceride than wild type cells. We now report that monoglyceride and triglyceride also accumulate in these strains. In mutant RZ60 (dgk-6) these compounds represent about 1 and 0.2%, respectively, of the total lipid fraction, while diglyceride represents 5-8% under most conditions. Monoglyceride accumulates predominantly in the outer membrane, while triglyceride builds up together with diglyceride in the cytoplasmic membrane. Under typical growth conditions about two-thirds of the diglyceride in E. coli arises in conjunction with synthesis of the membrane-derived oligosaccharides (Raetz, C.R.H., and Newman, K.F. (1979) J. Bacteriol. 137, 860-868). Inhibition of membrane-derived oligosaccharides (MDO) synthesis also curtails the accumulation of monoglyceride and triglyceride. However, there appears to be at least one other MDO-independent source of diglyceride and related metabolites. Since MDO synthesis is suppressed by high osmolarity (Kennedy, E.P. (1982) Proc. Natl. Acad. Sci. U.S. A. 79, 1092-1095), we have examined the effects of osmolarity on diglyceride accumulation in RZ60 (dgk-6). As expected, if MDO synthesis and diglyceride formation are coupled, the diglyceride level in RZ60 is higher at low osmolarity, while at high osmolarity the level of diglyceride is reduced to that observed in double mutants defective both in MDO synthesis and diglyceride kinase. Since dgk mutants do not grow at very low osmolarity, we have isolated several spontaneous phenotypic revertants that do. One class regains diglyceride kinase and has low diglyceride levels under all conditions. The other class remains defective in diglyceride kinase but tolerates higher diglyceride levels which amount to 13% of the total lipid during maximal induction of MDO synthesis at low osmolarity.

Cell Membrane↗