title: Studies on sucrose-phosphate synthase from rice leaves.
abstract: Sucrose-phosphate synthase (SPS, EC 2.4.1.14) biochemical properties and peptide composition have been analyzed in rice leaf seedlings. SPS was purified using DEAE-Sephacel chromatography, gel filtration on Sepharose 6B and anion exchange chromatography on Mono Q. At this stage two enzyme forms (SPS-I and -II) were separated. SPS-II was purified 90-fold; however, SPS-I presented a lower specific activity regarding the previous purification step and an unstable activity. Both enzyme forms had similar apparent Km values for Fru-6P but the SPS-I Km for UDP-Glc was ca. 10-fold higher than the SPS-II one. In addition, they differentiate in the capacity of being modulated by Glc-6-P and Pi: while SPS-II activity was inhibited by Pi and activated by Glc-6-P, SPS-I was not affected by either effectors. A native molecular mass of ca. 420 kDa was found by gel filtration. In SPS expression analysis using leaf rice and wheat germ SPS antibodies, a 116 kDa polypeptide was revealed in rice leaf extracts and no polypeptide was immunoactive in rice roots.
authors.affiliation: Centro de Investigaciones Biológicas, Fundación para Investigaciones Biológicas Aplicadas and PROBIOP-CONICET, Mar del Plata, Argentina.
authors.forename: G L
authors.initials: GL
authors.lastname: Salerno
authors.forename: G C
authors.initials: GC
authors.lastname: Pagnussat
authors.forename: H G
authors.initials: HG
authors.lastname: Pontis
mesh_terms: D005964:Glucosyltransferases / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D015151:Immunoblotting; D007527:Isoenzymes / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D012275:Oryza / Q000201:enzymology*; D018515:Plant Leaves / Q000201:enzymology; D010947:Plants, Toxic; D018724:Spinacia oleracea / Q000201:enzymology; D014026:Nicotiana / Q000201:enzymology; D014908:Triticum / Q000201:enzymology; D003313:Zea mays / Q000201:enzymology
chemical_list: D007527:Isoenzymes; D005964:Glucosyltransferases; C022698:sucrose-phosphate synthase