Liver

Golde, L.M.G. Van; Bergh, S.G. van den

doi:10.1007/978-1-4684-2832-2_2

Cited by 23 publications

(16 citation statements)

References 626 publications

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“…Irrespective of the pathway involved, degradation ultimately results in the formation of phosphocholine or choline from phosphatidylcholine. In liver, the predominant metabolic route by which choline is incorporated into phosphatidylcholine is the CDP-choline pathway [35,361. Another possibility for incorporation of choline into phosphatidylcholine is the exchange of choline with the base of another phosphoglyceride molecule [35].…”

Section: Con Version Of Lysophosphatidylcholine Into Phosphatidylcholmentioning

confidence: 99%

“…In liver, the predominant metabolic route by which choline is incorporated into phosphatidylcholine is the CDP-choline pathway [35,361. Another possibility for incorporation of choline into phosphatidylcholine is the exchange of choline with the base of another phosphoglyceride molecule [35]. This reaction was shown to occur in liver microsomal fractions, but is believed not to be important in the in vivo incorporation of choline into phosphatidylcholine [35,37].…”

Section: Con Version Of Lysophosphatidylcholine Into Phosphatidylcholmentioning

confidence: 99%

“…Another possibility for incorporation of choline into phosphatidylcholine is the exchange of choline with the base of another phosphoglyceride molecule [35]. This reaction was shown to occur in liver microsomal fractions, but is believed not to be important in the in vivo incorporation of choline into phosphatidylcholine [35,37]. It is also conceivable that after degradation of liposomal phosphatidylcholine within the lysosomes the resulting lysoderivative is reacylated by a lysophosphoglyceride-acyltransferase.…”

Section: Con Version Of Lysophosphatidylcholine Into Phosphatidylcholmentioning

confidence: 99%

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Uptake and processing of liposomal phospholipids by Kupffer cells in vitro

Dijkstra

Galen

Regts

et al. 1985

European Journal of Biochemistry

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We investigated the intracellular metabolic fate of choline-labeled phosphatidylcholines and sphingomyelin taken up by rat Kupffer cells in maintenance culture during interaction with large unilamellar liposomes composed of cholesterol, labeled choline-phospholipid and phosphatidylserine (molar ration 5 : 4 : 1).With both labeled compounds only small proportions of water-soluble radioactivity were found to accumulate in the cells and in the culture medium, suggesting limited phospholipid degradation. However, after a lag period of 30 min progressively increasing proportions of cell-associated liposomal phospholipid were found to be converted to cellular phospholipid, nearly all of which was phosphatidylcholine. This conversion as well as the limited release of watersoluble label from the cells was inhibited by the lysosomotropic agents ammonium chloride and chloroquine.With [Me-'4C]choline-labeled lysophosphatidylcholine, label was found to become cell-associated far in excess of an encapsulated liposomal label, [3H]inulin. Without a lag period virtually all of this was rapidly converted to phosphatidylcholine, a process which was not inhibited by the lysosomotropic agents..It is concluded that Kupffer cells, after endocytosis of liposomes, degrade the liposomal phospholipids effectively but reutilize the choline moiety for de novo synthesis of cellular phosphatidylcholine.

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Section: Con Version Of Lysophosphatidylcholine Into Phosphatidylcholmentioning

confidence: 99%

Section: Con Version Of Lysophosphatidylcholine Into Phosphatidylcholmentioning

confidence: 99%

Section: Con Version Of Lysophosphatidylcholine Into Phosphatidylcholmentioning

confidence: 99%

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Uptake and processing of liposomal phospholipids by Kupffer cells in vitro

Dijkstra

Galen

Regts

et al. 1985

European Journal of Biochemistry

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“…Mammals, for example, synthesize PtdSer by an exchange reaction with PtdEtn (9). However, PtdSer synthase is found in E. coli and indeed the structural gene for the E. coli enzyme has been cloned (10).…”

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confidence: 99%

Isolation of the yeast structural gene for the membrane-associated enzyme phosphatidylserine synthase.

Letts¹,

Klig²,

Bae-Lee³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

143

109

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The structural gene (CHOI) for phosphatidylserine synthase (CDPdiacylglycerol:L-serine O-phosphatidyltransferase, EC 2.7.8.8) was isolated by genetic complementation in Saccharomyces cerevmae from a bank of yeast genomic DNA on a chimeric plasmid. The cloned DNA (4.0 kilobases long) was shown to represent a unique sequence in the yeast genome. The DNA sequence on an integrative plasmid was shown to recombine into the CHOi locus, confwrming its genetic identity. The chol yeast strain transformed with this gene on an autonomously replicating plasmid had significantly increased activity of the regulated membrane-associated enzyme phosphatidylserine synthase. Partial purification of phosphatidylserine synthase from microsomes of this transformed strain confirmed that the membrane-bound enzyme was overproduced 6-to 7-fold as compared with the wild-type strain. The strain also synthesized the product phospholipid, phosphatidylserine, at an increased rate. The transformed strain had altered proportions of a variety of other phospholipids, suggesting that their synthesis is affected by the rate of synthesis of phosphatidylserine in yeast.The characterization of mutants altered in the synthesis of phospholipids has given considerable insight into the regulation of phospholipid metabolism in Escherichia coli and Saccharomyces cerevisiae (1, 2). Using yeast phospholipid mutants and the transformation techniques now available, it is possible to clone by complementation a number of the structural and regulatory genes involved in yeast lipid metabolism. These cloned genes can then be used as probes to study the synthesis, regulation, and assembly of the membrane-associated enzymes of phospholipid synthesis.The chol mutants of S. cerevisiae require either ethanolamine or choline for growth and are deficient in the synthesis of the phospholipid, phosphatidylserine (PtdSer) (3-5). PtdSer is the normal precursor for both phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (PtdCho). However, under conditions of ethanolamine or choline supplementation, chol mutants are able to use an alternative pathway described by Kennedy and Weiss (6) for the synthesis of PtdEtn and PtdCho (3-5). All chow mutants have very reduced levels of the enzyme phosphatidylserine synthase (CDPdiacylglycerol:L-serine 0-phosphatidyltransferase, EC 2.7.8.8). Thus, the CHOJ locus has the characteristics expected of the structural gene for this enzyme (4). Yeast PtdSer synthase is a regulated integral membrane protein (7,8) MATERIALS AND METHODS Strains. The haploid S. cerevsiae strain VAL2C (Mata leu2-3 leu2-112 ade6 chol) was derived from a cross of strain DC5 (Mata leu2-3 leu2-112 his3 cani-11, provided by J. Hicks) to strain VAL12 (MATa ade6 ural chol). Strain VAL12 was isoklted as an ethanolamine auxotroph from wild-type strain SHID SC (MATa ade6 ural). Strain 399 (UAA), lysl-1 (UAA), met8-1 (UAG), trpl-l (UAG), leu2 (UGA)] was obtained from G. Fink and wild-type strain S288C was used for the enzyme preparations. The E. coli strain used wa...

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“…February 10, 1981. 265 turnover rates were different for individual species of phospholipid molecules (Arvidson 1968;Van Golde and Van den Berg 1977;Akino and Shimojo 1970;Akino et al 1971). Although there is evidence that lung phosphatidylglycerol is structurally heterogenous Okano and Akino 1979), the metabolic heterogeneity of the lipid molecules has not been demonstrated.…”

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confidence: 99%