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At least 703 records · Page 39Linked to original sources
PubMed1999

Effect of processing conditions on phospholipase D activity of corn kernel subcellular fractions.

The influence of physicochemical conditions on the phospholipase D (PLD) activity of subcellular preparations of sweet corn (Zea mays L. cv. Peaches and Cream) kernels has been studied. The microsomal, mitochondrial, and cytosolic preparations of corn kernels possessed PLD activity albeit at varying proportions. The microsomal and cytosolic PLD activities were stimulated 2-fold between 5 and 15 degrees C. Ethanol had varying modulatory effects on PLD activity. By contrast, acetaldehyde was a potent inhibitor of PLD. As well, a naturally occurring C(6) aldehyde such as hexanal and an alcohol such as hexanol inhibited PLD activity efficiently. Divalent cations such as calcium chloride and magnesium chloride stimulated PLD activity at micromolar levels. Monovalent cations such as KCl and NaCl did not appear to affect PLD activity. Partial purification of PLD from the microsomal, mitochondrial, and cytosolic fractions separately revealed four major isoforms with relative molecular masses of 200, 140-150, 102-108, and 60-66 kDa. The importance of PLD in the maintenance of processed food quality is discussed.

Cytosol↗
PubMed1972

Subcellular fractionation by zonal centrifugation of glucose-repressed anaerobically grown Saccharomyces carlsbergensis.

1. Homogenates were prepared from sphaeroplasts of anaerobically grown, glucoserepressed Saccharomyces carlsbergensis, and the distributions of marker enzymes investigated after zonal centrifugation on sucrose gradients containing 2mm-MgCl(2). 2. These homogenates contained no detectable cytochrome c oxidase, succinate-cytochrome c oxidoreductase, succinate-ferricyanide oxidoreductase, l(+)-lactate-cytochrome c oxidoreductase or catalase. Cytochromes a+a(3) and c were not detected. 3. Zonal centrifugation of whole homogenates indicated complex density distributions of the sedimentable portions of NADH- and NADPH-cytochrome c oxidoreductases, adenosine triphosphatases (ATPases), adenosine pyrophosphatase (ADPase), pyrophosphatase and acid p-nitrophenyl phosphatase. Several different ATPases were distinguished on the basis of their sensitivities to oligomycin and ouabain. 4. Differential centrifugation of whole homogenates at 10(5)g-min left 80-90% of the protein, dithionite-reducible cytochrome b, acid hydrolases and pyrophosphatase in a supernatant (S(1)) together with 65 and 56% of the NADH- and NADPH-cytochrome c oxidoreductases respectively, 25% of the ATPases and 71% of the adenosine monophosphatase. 5. Further analysis of supernatant S(1) revealed the presence of a class of small particles containing NADPH-cytochrome c oxidoreductases and ATPases. 6. At least four different populations of large particles were distinguished. 7. Electron microscopy indicated that one of these corresponded to ;promitochondria' as described by other workers.

Adenosine Triphosphatases↗
PubMed1984

Subcellular fractionation of rat liver homogenates using two-polymer phase systems in a toroidal-coil centrifuge.

The principal organelles of rat liver homogenates were fractionated by two-phase partition chromatography using toroidal-coil centrifugation with a mixture of dextran T 500 and poly(ethylene glycol) 6000 in 0.26 M-sucrose containing 10 mM-sodium phosphate/phosphoric acid buffer, pH 7.4. The effects of varying the following parameters on organelle elution profiles, as reflected by their marker-enzyme activities, were studied: centrifuge speed; the composition and relative proportion of dextran-rich and poly(ethylene glycol)-rich phases in the eluent; flow rate; sample volume; homogenate concentration; helix diameter; tubing bore and the number of loops in the coil. Optimal resolution of the organelles was achieved with a toroidal coil of internal diameter 1.07 mm with a 4.55 mm helix diameter on a 0.42 m-diameter rotor running at 1000 rev./min. The eluent was prepared by combining, in a ratio of 93:7 (v/v), the poly(ethylene glycol)-rich upper phase and dextran-rich lower phase obtained from a phase mixture containing 3.3% (w/w) dextran and 5.4% (w/w) poly(ethylene glycol). The flow rate of the eluent was 14ml/h. Optimal conditions for separation of the organelles were evaluated. Resolution of plasma membrane and lysosomes was achieved. Separation of endoplasmic reticulum, which showed marked heterogeneity, from plasma membrane was also demonstrated. DNA and marker enzymes for peroxisomes, mitochondria and cytosol showed distinct elution profiles.

Animals↗
PubMed2005

Distribution of trace elements in subcellular fractions of three aquatic birds.

This study investigated the subcellular distribution of Cu, Zn, Cd and Ag in liver of mallard (Anas platyrhynchos), spot-billed duck (A. poecilorhyncha) and great cormorant (Phalacrocorax carbo) to better understand metal fractionation and dynamics in avian liver. Most of the total Cu, Zn, Cd and Ag were present in hepatocytosol, and their concentrations increased with total hepatic levels in all the three avian species. Copper, Zn and Cd in hepatocytosol were present mostly in metallothionein fractions (MTs), and Cu and Cd contents in this fraction were positively correlated with hepatocytosol levels in all the species. Silver was observed mostly in both high-molecular weight and MT fractions in hepatocytosol in mallard and great cormorant, whereas it was present in both low-molecular weight and MT fractions in spot-billed duck, suggesting that distribution of Ag in the hepatocytosol was species-specific. The elution profile of metals in MT fractions revealed six metallic peaks in mallard and spot-billed duck, and three peaks in great cormorant, implying the presence of multiple MT isoforms in the liver of these avian species. The present study demonstrated that MTs are closely associated with metal regulation, especially Cu and Cd, in these three aquatic birds.

Animals↗