Relation of Rheological Properties with Starch Components among Glutinous,Sticky, Less-sticky Non-glutinous Rice Starches

Varoius piericidin analogues (PS-I, -II and -III in Fig. 2) were synthesized from three 4-acetoxy-6-formylpyridines by Wittig reaction to determine the structure-activity relationships. New type inhibitors, 5-alkenyl-2, 3-dimethoxy-4-hydroxy-6-methylpyridines (PS-IV) were synthesized by intramolecular cyclization.     

Aggregated Forms of Glucose-6-phosphate Dehydrogenase from Cultured Rice Plant Cells

Multiple molecular forms of glucose-6-phosphate dehydrogenaseincluding aggregated ones were observed in rice plant suspensioncultures by disc electrophoresis. By sucrose density gradientcentrifugation, the enzyme was resolved into three componentswith the sedimentation coefficients of 42.5, 23 and 6, respectively.The first two components were dissociated into the third componentin the presence of KC1, NADP⁺ and NADPH. These three componentswere interconvertible molecular species. (Received September 16, 1980; Accepted December 19, 1980)     

Structure and Function of the Golgi Complex in Rice Cells (II. Purification and Characterization of Golgi Membrane-Bound Nucleoside Diphosphatase)

The gene coding for phytoene desaturase of the bacterium Erwinia uredovora (crtI) was inserted into the chromosome of the cyanobacterium Synechococcus PCC7942 strain R2-PIM8. For expression of crtI in the heterologous host, two constructs with different promoters were introduced into Synechococcus. In the first, crtI was fused to the 5[prime] region of the psbA gene of the xanthophycean microalga Bumilleriopsis filiformis. The second construct carried crtI inserted downstream of the neomycin phosphotransferase II gene (nptII) from the transposon Tn5. Expression of crtI under the control of the respective promoter was shown by immunodetection of the gene product. The functionality of the heterologously expressed phytoene desaturase CRTI in the transformants was demonstrated by enzymic assays. The transformants acquired very strong resistance toward the bleaching herbicide norflurazon.     

Structure and Function of the Golgi Complex in Rice Cells: Characterization of Golgi Membrane Glycoproteins

The structure and synthesis of the saccharide chains of Golgimembrane glycoproteins in suspension-cultured rice (Oryza sativaL.) cells were studied. Peanut lectin (PNA) and Ulex europaeuslectin-I (UEA-I) have high affinity for typical O-linked saccharidechains and both recognized the saccharide chains of rice Golgimembrane glycoproteins. These glycoproteins were also sensitiveto alkali and to O-glycanase. These results indicate that theGolgi membrane glycoproteins have O-linked saccharide chains.Brefeldin A, a specific inhibitor of Golgi-mediated secretion,induced morphological changes in Golgi complexes and preventedthe synthesis of the saccharide chains of the membrane glycoproteinsthat could be recognized by PNA and UEA-I. These glycoproteinswere typically localized in all compartments of the Golgi complex.Monensin can arrest the transport of secretory proteins frommedial to trans Golgi compartments but did not affect the formationand localization of the Golgi membrane glycoproteins. Tunicamycin,an inhibitor of the synthesis of N-linked saccharide chains,did not inhibit the synthesis of the saccharide chains of theseGolgi membrane glycoproteins. These results strongly suggestthat the synthesis of O-linked saccharide chains of Golgi membraneglycoproteins is initiated in the cis Golgi compartment. (Received September 24, 1992; Accepted June 4, 1993)     

Alcohol Dehydrogenase from Cultured Rice Cells

Rice cells in suspension culture had high alcohol dehydrogenaseactivity during the logarithmic growth phase (3rd to 5th day).Ethanol was accumulated both in the cells and in the medium.The highest amount of ethanol was accumulated on the 4th dayin cells (10 µmoles/g fresh weight) and during the stationarygrowth phase (8th day) (180 mM, ca. 1%) in the medium. The enzymewas isolated from the cell extract and purified 36-fold witha 14% yield by ammonium sulfate fractional precipitation, andchromatography on DEAE-Sephadex, Sephadex G-150 and Blue Dextran-Sepharose.The purified enzyme was homogeneous, as judged by its sedimentationvelocity, and poly acrylamide gel, starch gel and SDS-polyacrylamidegel electrophoreses. Its molecular weight was 76,000 distributedin two, identical 37,000 subunits. The isoelectric point wasat pH 5.5. The enzyme contained 2.1 g atoms of zinc, 12 freeSH groups and 3 to 4 SS bonds per molecule. The pH optimum forethanol oxidatioa was pH 9.5 and for acetaldehyde reductionpH 6.0. The K_m values for ethanol, NAD^$, acetaldehyde and NADHwere 64.5 mM, 47.1 µM, 1.3 mM and 9.5 µM. The aminoacid composition, substrate specificity, and the effects ofchelators, SH reagents and sugar metabolic intermediates alsoare reported. (Received August 25, 1981; Accepted December 7, 1981)     

Isolation and Characterization of Golgi Membranes from Suspension-cultured Cells of Rice (Oryza sativa L.)

The isolation of Golgi membranes from suspension-cultured cellsof rice (Oryza sativa L.) was attempted by linear glycerol densitygradient centrifugation. When "burst" membranes in the pelletobtaind after differential centrifugation at 100,000 ? g weresuspended in 20% (w/w) glycerol in 50 mM malate-NaOH (pH 6.0)and loaded onto a linear density gradient of glycerol, whichextended from 30 to 80% (w/w) in 1 mM EDTA in 50 mM glycylglycine-NaOH(pH 7.5), IDPase, a marker enzyme for Golgi membranes, was separatedfrom other membrane markers on the glycerol gradient. In addition,UDPase and GDPase activities overlapped with the peak fractionof IDPase activity. Furthermore, membrane glycoproteins in eachfraction were characterized by lectin-peroxidase staining. ConcanavalinA and lentil lectin, which have the ability to bind to the high-mannosetype of oligosaccharide, bound to glycoproteins distributedin ER membrane fractions, while wheat germ lectin, castor beanlectin, peanut lectin, and Ulex europaeus lectin-I which recognizethe complex type and/or the mucin type of oligosaccharides interactedwith glycoproteins in the Golgi membrane fractions but not withthose in the ER membrane. These results strongly suggest thatthe oligosaccharide structures of glycoproteins in the ER membraneare of the high-mannose type, whereas glycoproteins in the Golgimembrane have modified N-linked and/or O-linked oligosaccharidechains. (Received November 9, 1988; Accepted October 17, 1989)     

Studies on Q-Enzyme of Rice Plant

Purification of Q-enzyme prepared from the extract of rice seed at the milky stage employing precipitation by lead acetate, fractionation by ammonium sulfate and chromatography on hydroxylapatite was carried out. The highly purified preparation of Q-enzyme was nearly homogeneous in electrophoresis, chromatography and solubility, and was nearly free from amylase, maltase, isoamylase, phosphorylase and phosphatase activities. Some of the physico-chemical and enzymic properties of the preparation were also investigated.