title: Biocatalytic role of potato starch synthase III for α-glucan biosynthesis in Synechocystis sp. PCC6803 mutants.
abstract: A potato starch synthase III (PSSIII) was expressed in the Synechocystis mutants deficient in either glycogen synthase I (M1) or II (M2) to replenish α-(1,4) linkage synthesizing activity, resulting in new mutants, PM1 and PM2, respectively. These mutants were applied to study the role of exogenous plant starch synthase for starch/glycogen biosynthesis mechanism established in the cyanobacteria. The remaining glycogen synthase genes in PM1 and PM2 were further disrupted to make the mutants PM12 and PM21 which contained PSSIII as the sole glycogen/starch synthase. Among wild type and mutants, there were no significant differences in the amount of α-glucan produced. All the mutants harboring active PSSIII produced α-glucans with relatively much shorter and less longer α-1,4 chains than wild-type glycogen, which was exactly in accordance with the increase in glycogen branching enzyme activity. In fact, α-glucan structure of PM1 was very similar to those of PM12 and PM21, and PM2 had more intermediate chains than M2. This result suggests PSSIII may have distributive elongation property during α-glucan synthesis. In conclusion, the Synechocystis as an expression model system of plant enzymes can be applied to determine the role of starch synthesizing enzymes and their association during α-glucan synthesis.
authors.affiliation: Department of Food Science & Technology and Carbohydrate Bioproduct Research Center, Sejong University, 98 Gunja-Dong, Gwangjin-Gu, Seoul 143-747, South Korea. Electronic address: shyoo@sejong.ac.kr.
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Yoo
authors.affiliation: Department of Food Science & Biotechnology, College of BioNano Technology, Gachon University, Seongnam 461-701, South Korea.
authors.forename: Byung-Hoo
authors.initials: BH
authors.lastname: Lee
authors.affiliation: Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Botany, Iowa State University, Ames, IA 50011, USA.
authors.forename: Shayani D N
authors.initials: SD
authors.lastname: Perris
authors.affiliation: Department of Botany, Iowa State University, Ames, IA 50011, USA.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Spalding
authors.affiliation: Department of Nanochemistry, College of BioNano Technology, Gachon University, Seongnam 461-701, South Korea.
authors.forename: Sang Yun
authors.initials: SY
authors.lastname: Han
authors.affiliation: Department of Food Science and Human Nutrition, Iowa State University, Ames, IA 50011, USA.
authors.forename: Jay-lin
authors.initials: JL
authors.lastname: Jane
mesh_terms: D055162:Biocatalysis; D015870:Gene Expression; D023061:Gene Order; D005822:Genetic Vectors / Q000235:genetics; D005936:Glucans / Q000096:biosynthesis*; D006006:Glycogen Synthase / Q000235:genetics; D009154:Mutation; D011198:Solanum tuberosum / Q000201:enzymology*; D013214:Starch Synthase / Q000378:metabolism*; D046939:Synechocystis / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005936:Glucans; D006006:Glycogen Synthase; D013214:Starch Synthase
keywords: Glycogen branching enzyme; Glycogen synthase; Potato starch synthase III; Synechocystis sp. PCC6803; α-Glucan