ARS | Publication request: SUGARBEET ROOT SUCROSE SYNTHASE ISOFORMS ARE TETRAMERS COMPOSED OF VARYING RATIOS OF TWO PUTATIVE SUBUNITS.

Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 26, 2001
Publication Date: N/A

Technical Abstract: Sucrose synthase (UDP-D-Glc: D-Fru 2-alpha-glucosyltransferase, EC 2.4.1.13) catalyzes the transfer of a glucose residue from sucrose to uridine 5'-diphosphate (UDP) to yield UDP-glucose and fructose. Sucrose synthase is the major sucrolytic enzyme in sugarbeet root and may play a role in the regulation of sink strength and carbon partitioning to the root. Sucrose synthase was isolated from mature sugarbeet root tissue by a combination of ammonium sulfate fractionation, size exclusion chromatography, ion chromatography and affinity chromatography. Polyclonal antibodies were raised against the purified enzyme and used for subsequent Western analysis of the protein at different stages of sugarbeet root development. Native sucrose synthase had an apparent molecular weight of 320 kDa. SDS-PAGE revealed the presence of two distinct protein bands with apparent molecular weights of approximately 84 and 86 kDa. The native protein, therefore, is a tetramer. Both subunits were found to have a similar amino acid composition and may arise from separate, but very similar genes or from different posttranslational modification of a single gene product. Different isoforms of sucrose synthase were found throughout root development due to differences in the relative proportion of the two subunits. The smaller putative subunit predominated in sucrose synthase isoforms isolated from young sugarbeet roots; the larger putative subunit predominated in sucrose synthase isoforms isolated from mature sugarbeet roots.