Studies on Phospholipid-synthesizing Enzyme Activities during the Growth of Etiolated Cucumber Cotyledons

Macher, Bruce A.; Brown, Christine P.; McManus, T.T.; Mudd, J.B.

doi:10.1104/pp.55.1.130

Cited by 20 publications

(2 citation statements)

References 25 publications

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“…1) was somewhat surprising. It has been reported that monoacylglycerols were labeled from [U-'4C]glycerol in crambd oil bodies (11) and from [1-'~C]glycerol-3-phosphate in microsomes from safflower {26) and avocado (27) and in cucumber cotyledon homogenates (28), but in most cases the extent of labeling was relatively low. In a recent study, however, relatively high proportions of labeled monoacylglycerols were formed from [1-"C]oleoyl-CoA in homogenate, oil body and soluble fractions from developing mustard seeds (12).…”

Section: Resultsmentioning

confidence: 99%

Acyltransferases in subcellular fractions of developing seeds of rape (Brassica napus L.)

Murphy

Mukherjee²

1987

Lipids

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Acyltransferase activities responsible for the transfer of oleoyl moieties from oleoyl-CoA to various lipids have been examined in subcellular fractions of developing seeds of rape, Brassica napus L. In the absence of exogenous acyl acceptors, the microsomal and oil body fractions transferred oleoyl moieties mostly to phosphatidylcholines and phosphatidic acids, although there was substantial incorporation of the oleoyl moieties into monoacylglycerols, diacylglycerols and triacylglycerols. The soluble (150,000-g supernatant) fraction incorporated oleoyl moieties mainly into the neutral lipids (monoacylglycerols and diacylglycerols) and also exhibited a relatively high acyl-CoA hydrolase activity. In the presence of the exogenous acyl acceptors, lysophosphatidylcholine and lysophosphatidic acid, both microsomal and oil body fractions transferred most of the oleoyl moieties to phosphatidylcholines and phosphatidic acids, respectively. Other lysophospholipids, such as lysophosphatidylethanolamine and lysophosphatidylinositol, were not very effective as acyl acceptors, nor were glycerol-3-phosphate, monoacylglycerols or diacylglycerols. In contrast, the soluble fraction showed little or no stimulation of acyltransfer in the presence of exogenous lysophospholipids but was able to utilize, to some extent, exogenous monoacylglycerols and diacylglycerols as acyl acceptors.

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Section: Resultsmentioning

confidence: 99%

Acyltransferases in subcellular fractions of developing seeds of rape (Brassica napus L.)

Murphy

Mukherjee²

1987

Lipids

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“…Thus, 1-0-hexadecyl-2-acylglycerols as well as 1 -0-[(2)-9'-octadecenyl]-2-acylglycerols isolated from photomixotrophc rape cells contained predominantly palmitoyl and oleoyl moieties at sn-2 position. Since the formation of diacylglycerols via the monoacylglycerol pathway does not seem to occur in plant tissues [31] it is quite likely that 1-0-alkyl-2-acylglycerols were synthesized via alkyl lysophosphatidic acid intermediates, as suggested for the phosphorylation of monoacylglycerols in cucumber cotyledons [32]. On the other hand, it cannot be ruled out that acyl moieties may be transferred directly to alkylglycerols by the action of an acylhydrolase that can catalyze acyltransfer as well [33].…”

Section: Substrates Added Tomentioning

confidence: 99%

Ether glycerolipids: novel substrates for studying specificity of enzymes involved in glycerolipid biosynthesis in higher plants

Weber¹,

Benning²

1985

European Journal of Biochemistry

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Ether glycerolipids, predominantly alkylacylglycerols and alkylacylglycerophosphocholines, are synthesized in photomixotrophc rape (Brassica napus) suspension cells from various exogenous monoalkylglycerols. The stereospecific distribution of acyl moieties was studied in these ether glycerolipids with regard to chain-length and degree of unsaturation of alkyl moieties and compared with the distribution of acyl moieties in the corresponding endogenous acyl glycerolipids. The results show the following : (1) Alkylacylglycerophosphocholines replaced up to one-half of the corresponding physiological membrane lipids, i.e. diacylglycerophosphocholines, without changing the total amount of cholineglycerophospholipids as compared to untreated cells. (2) The composition of acyl moieties in total lipids of rape cells was practically unaltered by fatty acids derived via oxidative cleavage from the various alkyl moieties of ether glycerolipids. (3) In 1-0-alkyl-2-acylglycerols derived from exogenous alkylglycerols and in endogenous 1,2-diacylglycerols compositions of acyl moieties were found to be different indicating that different pathways were operative in the biosynthesis of these two neutral glycerolipids. (4) Enzymes involved in synthesizing molecular species of I-0-alkyl-2-acylglycerophosphocholines or 2-O-alkyl-lacylglycerophosphocholines as well as 1,2-diacylglycerophosphocholines showed similar specificities with regard to chain-length and degree of unsaturation of both alkyl and corresponding acyl moieties. Thus, ether glycerolipids formed by plant cells from exogenous alkylglycerols are suitable metabolites for studying the specificity of enzymes involved in the biosynthesis of glyerolipids.Higher plants do not contain appreciable amounts of ether lipids [l -31. Yet, plant cells and plant cell microsomes are able to synthesize ether glycerolipids from suitable exogenous precursors [4-71. Thus, rape (Brassica napus) cells in culture have been found to convert exogenous 1 -0-alkylglycerols predominantly to l-O-alkyl-2-acylglycerols, 1-0-alkyl-3-acylglycerols and 1 -O-alkyl-2-acylglycerophosphocholines [8, 91. The alkyl moieties of ether glycerolipids have been found to be metabolically quite stable, as compared to the corresponding acyl moieties of acyl glycerolipids [lo]. Therefore, lipids containing alkyl moieties, rather than those containing only acyl moieties, may be useful as markers in studies on the biosynthesis and turnover of glycerolipids in plant cells. Using alkylglycerols as substrates we have studied the stereospecificity of enzymes involved in the formation of complex glycerolipids. MATERIALS AND METHODSChemicals and syntheses rac-1-0-Alkylglycerols were prepared following established procedures [I 1, 121. Similarly,

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Etherlipide als Substrate zur Untersuchung der Spezifität von Enzymen der Glycerolipid‐Biosynthese in höheren Pflanzen

Weber¹

1985

Fette, Seifen, Anstrichm.

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Etherglycerolipide, hauptsachlich Alkylacylglycerine und Alkylacylglycerophosphocholine, werden von photomixotrophen Rapszellen (Brclssica nupus) in Suspensionskultur aus exogenen Monoalkylglycerinen gebildet. Die stereospezifische Verteilung der Acyl-Reste in diesen Etherglycerolipiden wurde in Abhhgigkeit von Kettenlhge und Grad der Unsattigung der Alkyl-Reste untersucht und verglichen mit derverteilungder Acyl-Reste in den entsprechenden endogenen Acylglycerolipiden. Die Ergebnisse lassen sich folgendermden zusammenfassen: (a) Alkylacylglycerophosphocholine konnten die entsprechenden physiologischen Membranlipide, i. e. Diacylglycerophosphocholine, bis zur Hdfte ersetzen,wobei die Gesamtmenge der Cholinglycerophospholipide verglichen mit der in unbehandelten Zellen konstant blieb. (b) DieZusammensetzung derAcyl-restein den Gesamtlipiden der Rapszellen wurde durch Fettsauren aus der oxidativen Spaltung der verschiedenen Etherglycerolipide praktisch nicht veriindert. (c) In 1 -0 Alkyl-2-acylglycerinen aus exogenen Alkylglycerinen und in endogenen 12-Diacylglycerinen wurden unterschiedliche Zusammensetzungen von Acyl-Resten gefunden, was auf unterschiedliche Biosyntheswege bei der Entstehung dieser beiden neutralen Lipide hinweist. (d) Enzyme,die an der Biosynthese molekularer Species von 1-0Alkyl-2-acyloder 2-OAlkyl-1acylglycerophosphocholinen sowie 12-Diacylglycerophosphocholinen beteiligt sind, zeigen W i c h e Spezifitaten in bezug auf Kettenlhge und Grad der Unsattigung der Alkyl-sowie der entsprechenden Acyl-Reste. Daher scheinen Etherglycerolipide, die in Pflanzenzellen aus exogenen Alkylglycerinen gebildet wurden, geeignete Metaboliten fur die Untersuchung der Spezifitat von Enzymen der Glycerolipid-Biosynthese zu sein.

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Studies on Phospholipid-synthesizing Enzyme Activities during the Growth of Etiolated Cucumber Cotyledons

Cited by 20 publications

References 25 publications

Acyltransferases in subcellular fractions of developing seeds of rape (Brassica napus L.)

Acyltransferases in subcellular fractions of developing seeds of rape (Brassica napus L.)

Ether glycerolipids: novel substrates for studying specificity of enzymes involved in glycerolipid biosynthesis in higher plants

Etherlipide als Substrate zur Untersuchung der Spezifität von Enzymen der Glycerolipid‐Biosynthese in höheren Pflanzen

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