Remodeling of rat hepatocyte phospholipids by selective acyl turnover

Schmid, Patricia C.; Johnson, Sandra; Schmid, Harald H.O.

doi:10.1016/s0021-9258(18)92754-7

Cited by 60 publications

(6 citation statements)

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“…Exchange of 180 has been used for mechanistic studies of enzyme-catalyzed hydrolyses involving phosphoryl (Van Etten & Risley, 1978; Bock & Cohn, 1978) and acyl (Wells, 1971; van Heusden & van den Bosch, 1979; Lombardo et al, 1986;Fanni et al, 1989;Schmid et al, 1988) groups and for studies of acyl group deacylation-reacylation cycles (Kuwae et al, 1987(Kuwae et al, , 1990, Schmid et al, 1991. Previous studies of acyl group hydrolysis involved phospholipids.…”

Section: Discussionmentioning

confidence: 99%

Regulation of fatty acid oxygen-18 exchange catalyzed by pancreatic carboxylester lipase. 1. Mechanism and kinetic properties

Muderhwa

Schmid²,

Brockman³

1992

Biochemistry

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The exchange of 18O between H2O and long-chain free fatty acids is catalyzed by pancreatic carboxylester lipase (EC 1.1.1.13). For palmitic, oleic, and arachidonic acid in aqueous suspension and for 13,16-cis,cis-docosadienoic acid (DA) in monomolecular films, carboxyl oxygens were completely exchanged with water oxygens of the bulk aqueous phase. With enzyme at either substrate or catalytic concentrations in the argon-buffer interface, the exchange of DA oxygens obeyed a random sequential mechanism, i.e., 18O,18O-DA in equilibrium with 18O,16O-DA in equilibrium with 16O,16O-DA. This indicates that the dissociation of the enzyme-DA complex is much faster than the rate-limiting step in the overall exchange reaction. Kinetic analysis of 18O exchange showed a first-order dependence on surface enzyme and DA concentrations, i.e., the reaction was limited by the acylation rate. The values of kcat/Km, 0.118 cm2 pmol-1 s-1, for the exchange reaction was comparable to that for methyl oleate hydrolysis and 5-fold higher than that for cholesteryl oleate hydrolysis in monolayers [Bhat, S., & Brockman, H. L. (1982) Biochemistry 21, 1547]. Thus, fatty acids are good "substrates" for carboxylester lipase. With substrate levels of carboxylester lipase in the interfacial phase, the acylation rate constant kcat/Km was 200-fold lower than that obtained with catalytic levels of enzyme. This suggests a possible restriction of substrate diffusion in the protein-covered substrate monolayer.

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Section: Discussionmentioning

confidence: 99%

Regulation of fatty acid oxygen-18 exchange catalyzed by pancreatic carboxylester lipase. 1. Mechanism and kinetic properties

Muderhwa

Schmid²,

Brockman³

1992

Biochemistry

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“…Since saturated PC species are reported to be enriched in the plasma membrane (as opposed to the ER) (Keenan and Morre, 1970), COPI-coated vesicle-mediated lipid sorting does not appear to contribute to this steady-state distribution. Most likely, remodeling of lipid species accounts for the higher degree of lipid saturation at the plasma membrane (MacDonald and Sprecher, 1991;Schmid et al, 1991;Schneiter et al, 1999). The relative distribution of the various SM species in donor membranes and COPI vesicles was found to be significantly changed in both the CHO and the rat liver system.…”

Section: Segregation Of Molecular Speciesmentioning

confidence: 97%

Evidence for Segregation of Sphingomyelin and Cholesterol during Formation of Copi-Coated Vesicles

Brügger

Sandhoff

Wegehingel

et al. 2000

The Journal of Cell Biology

211

158

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In higher eukaryotes, phospholipid and cholesterol synthesis occurs mainly in the endoplasmic reticulum, whereas sphingomyelin and higher glycosphingolipids are synthesized in the Golgi apparatus. Lipids like cholesterol and sphingomyelin are gradually enriched along the secretory pathway, with their highest concentration at the plasma membrane. How a cell succeeds in maintaining organelle-specific lipid compositions, despite a steady flow of incoming and outgoing transport carriers along the secretory pathway, is not yet clear. Transport and sorting along the secretory pathway of both proteins and most lipids are thought to be mediated by vesicular transport, with coat protein I (COPI) vesicles operating in the early secretory pathway. Although the protein constituents of these transport intermediates are characterized in great detail, much less is known about their lipid content. Using nano-electrospray ionization tandem mass spectrometry for quantitative lipid analysis of COPI-coated vesicles and their parental Golgi membranes, we find only low amounts of sphingomyelin and cholesterol in COPI-coated vesicles compared with their donor Golgi membranes, providing evidence for a significant segregation from COPI vesicles of these lipids. In addition, our data indicate a sorting of individual sphingomyelin molecular species. The possible molecular mechanisms underlying this segregation, as well as implications on COPI function, are discussed.

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“…Apart from such species differences established by de novo synthesis of the various lipid classes (Samborski et al, 1990), species differences may also be established later, by the salvage/Kennedy pathway for PE and PC synthesis from local pools of DAG species produced in the Golgi apparatus (Kearns et al, 1997). Furthermore, pathways may exist to generate specific molecular species by remodeling the acyl chain composition of existing lipids (Mac-Donald and Sprecher, 1991;Schmid et al, 1991); different molecular species may have different rates of turnover (Ousley and Morell, 1992), or may be transported with different efficiency (Heikinheimo and Somerharju, 1998).…”

Section: Phospholipid Class-specific Differences In the Degree Of Acyl Chain Saturationmentioning

confidence: 99%

Electrospray Ionization Tandem Mass Spectrometry (Esi-Ms/Ms) Analysis of the Lipid Molecular Species Composition of Yeast Subcellular Membranes Reveals Acyl Chain-Based Sorting/Remodeling of Distinct Molecular Species En Route to the Plasma Membrane

Schneiter

Brügger

Sandhoff

et al. 1999

The Journal of Cell Biology

447

409

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Nano-electrospray ionization tandem mass spectrometry (nano-ESI-MS/MS) was employed to determine qualitative differences in the lipid molecular species composition of a comprehensive set of organellar membranes, isolated from a single culture of Saccharomyces cerevisiae cells. Remarkable differences in the acyl chain composition of biosynthetically related phospholipid classes were observed. Acyl chain saturation was lowest in phosphatidylcholine (15.4%) and phosphatidylethanolamine (PE; 16.2%), followed by phosphatidylserine (PS; 29.4%), and highest in phosphatidylinositol (53.1%). The lipid molecular species profiles of the various membranes were generally similar, with a deviation from a calculated average profile of ∼± 20%. Nevertheless, clear distinctions between the molecular species profiles of different membranes were observed, suggesting that lipid sorting mechanisms are operating at the level of individual molecular species to maintain the specific lipid composition of a given membrane. Most notably, the plasma membrane is enriched in saturated species of PS and PE. The nature of the sorting mechanism that determines the lipid composition of the plasma membrane was investigated further. The accumulation of monounsaturated species of PS at the expense of diunsaturated species in the plasma membrane of wild-type cells was reversed in elo3Δ mutant cells, which synthesize C24 fatty acid-substituted sphingolipids instead of the normal C26 fatty acid-substituted species. This observation suggests that acyl chain-based sorting and/or remodeling mechanisms are operating to maintain the specific lipid molecular species composition of the yeast plasma membrane.

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Remodeling of rat hepatocyte phospholipids by selective acyl turnover

Cited by 60 publications

References 0 publications

Regulation of fatty acid oxygen-18 exchange catalyzed by pancreatic carboxylester lipase. 1. Mechanism and kinetic properties

Regulation of fatty acid oxygen-18 exchange catalyzed by pancreatic carboxylester lipase. 1. Mechanism and kinetic properties

Evidence for Segregation of Sphingomyelin and Cholesterol during Formation of Copi-Coated Vesicles

Electrospray Ionization Tandem Mass Spectrometry (Esi-Ms/Ms) Analysis of the Lipid Molecular Species Composition of Yeast Subcellular Membranes Reveals Acyl Chain-Based Sorting/Remodeling of Distinct Molecular Species En Route to the Plasma Membrane

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