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Biomedical subjects

T S Moore

Publications and source records attributed to T S Moore.

44 records · Page 3Linked to original sources
PubMed1975

Phosphatidylserine synthesis in castor bean endosperm.

Phosphatidylserine synthesis by the endoplasmic reticulum fraction isolated from castor bean (Ricinus communis var. Hale) endosperm was assayed by measuring the incorporation of (14)C-l-serine into chloroform-soluble material. Both phosphatidylserine and phosphatidylethanolamine were identified as products. The incorporation required calcium ions and showed an optimum pH of 7.8 in 2 mm CaCl(2). Phosphatidylethanolamine and CDP-diglyceride stimulated the reaction only about 40 to 50% and primary alcohols had relatively little effect on the incorporation. These and other results suggest the synthesis of phosphatidylserine in this tissue occurs by an exchange reaction but the relative roles of phospholipase D and phosphatidylethanolamine: l-serine phosphatidyltransferase remain to be elucidated.

Journal Article↗
PubMed1974

Isolation and characterization of organelles from soybean suspension cultures.

Whole homogenates from cells of Glycine max grown in suspension culture were centrifuged on linear sucrose gradients. Assays for marker enzymes showed that distinct peaks enriched in particular organelles were separated as follows: endoplasmic reticulum (density 1.10 g/cm(3), NADH-cytochrome-c reductase), Golgi membranes (density 1.12 g/cm(3), inosine diphosphatase), mitochondria (density 1.18-1.19 g/cm(3), fumarase, cytochrome oxidase) and microbodies (density 1.21-1.23 g/cm(3), catalase). In cells which had ceased to grow (stationary phase) only a single symmetrical catalase peak at density 1.23 g/cm(3) was observed on the sucrose gradient. During the phase of cell division and expansion a minor particulate catalase component of lighter density was present; its possible significance is discussed.

Journal Article↗
PubMed1974

Phosphatidylglycerol synthesis in castor bean endosperm: kinetics, requirements, and intracellular localization.

The synthesis of phosphatidylglycerol in castor bean (Ricinus communis var. Hale) endosperm tissue was found to be located in both the endoplasmic reticulum and mitochondrial fractions separated on sucrose density gradients. The enzyme of both fractions attained maximum activity at 5 mm Mn(2+), 0.075% Triton X-100, and pH 7.3. The addition of dithiothreitol produced little effect, but sulfhydryl inhibitors reduced activity in both systems. Cytidine diphosphate-diglyceride exhibited an apparent Michaelis constant for the endoplasmic reticulum enzyme of 2.8 mum and for the mitochondrial enzyme of 2.0 mum; the maximum reaction rate was achieved at about 20 mum. For the second substrate, glycerol-phosphate, the apparent Michaelis constant for both fractions was about 50 mum and maximum velocity was reached at 400 mum. The specific activity of the mitochondrial enzyme was generally twice that of the endoplasmic reticulum.

Journal Article↗
PubMed1973

Endoplasmic reticulum as the site of lecithin formation in castor bean endosperm.

The properties of a discrete membranous fraction isolated on sucrose gradients from castor bean endosperm have been examined. This fraction was previously shown to be the exclusive site of phosphorylcholine-glyceride transferase. The distribution of NADPH-cytochrome c reductase and antimycin insensitive NADH-cytochrome c reductase across the gradient followed closely that of the phosphorylcholine-glyceride transferase. This fraction also had NADH diaphorase activity and contained cytochromes b(5) and P 450. On sucrose gradients containing 1 mM EDTA this fraction had a mean isopycnic density of 1.12 g/cm(3) and sedimented separately from the ribosomes; electron micrographs showed that it was comprised of smooth membranes. When magnesium was included in the gradients to prevent the dissociation of membrane-bound ribosomes, the isopycnic density of the membrane fraction with its associated enzymes was increased to 1.16 g/cm(3) and under these conditions the electron micrographs showed that the membranes had the typical appearance of rough endoplasmic reticulum. Together these data show that the endoplasmic reticulum is the exclusive site of lecithin formation in the castor bean endosperm and establish a central role for this cytoplasmic component in the biogenesis of cell membranes.

Cell Fractionation↗
PubMed1973

An extracellular macromolecular complex from the surface of soybean suspension cultures.

A cell-free, insoluble cell wall fraction is described which floats on the surface of suspension cultures of Glycine max L. Merrill var. Acme cells. Its accumulation is governed by both the shaking speed and the medium volume, a shaking speed of 110 to 120 revolutions per minute with a medium volume of about 100 to 120 milliliters in a 250-milliliter flask being optimal. Various factors which could control the accumulation of the complex were tested and are discussed, and scanning electron micrographs of the complex being released from the cell surface are presented.The composition of the complex by weight is 46% galacturonic acid, 36% protein, 11% lignin (apparent), 4.4% arabinose, 2% ash, and 0.5% methyl ester. Evidence for an intimate relationship between the uronic acid and protein fractions is presented. The protein contains hydroxyproline, and the bulk of it is tightly bound to the complex, although a portion can be removed with high salt treatments.

Journal Article↗
PubMed1973

Enzymes of phospholipid metabolism in the endoplasmic reticulum of castor bean endosperm.

The intracellular location of several enzymes concerned with phospholipid metabolism was investigated by examining their distribution in organelles separated on sucrose gradients from total homogenates of castor bean (Ricinus communis var. Hale) endosperm. The enzymes phosphatidic acid phosphatase, CDP-diglyceride-inositol transferase, and phosphatidyletha-nolamine-l-serine phosphatidyl transferase were all primarily or exclusively confined to membranes of the endoplasmic reticulum. These results and those reported previously on lecithin synthesis establish a major role of the endoplasmic reticulum in phospholipid and membrane synthesis in plant tissues.

Journal Article↗
PubMed1972

Effects of cytokinins on the respiration of soybean callus tissue.

A technique which incorporates a brief blending step to disperse callus tissue into small clumps of cells was developed, and the effects of cytokinins on respiration of soybean (Glycine max [L.] Merrill var. Acme) callus tissue prepared in this way were studied. Adenine alone did not affect respiration, but kinetin and zeatin showed effects correlating with their reported effects on growth of this tissue; after about 3 hours both hormones promoted respiration at concentrations which promote growth, while kinetin, but not zeatin, also exhibited inhibition at higher concentrations. Studies with 2,4-dinitrophenol led to the suggestion that although the respiration of this tissue is largely under the control of ATP levels, kinetin does not exert its control on respiration through effects on ATP levels or oxidative phosphorylation during the monitoring period. Further inhibitor and substrate studies provided evidence that the promotion of respiration by kinetin results from an increase in substrate entering the tricarboxylic acid cycle, perhaps by an effect on pyruvate metabolism.The inhibition of respiration by high concentrations of kinetin is partially due to effects on oxidative phosphorylation or ATP utilization, but 70% of the inhibition cannot be attributed to this.

Journal Article↗