Identification of a novel starch synthase III from the picoalgae Ostreococcus tauri.
Biochimie
; 133: 37-44, 2017 Feb.
Article
in En
| MEDLINE
| ID: mdl-28003125
ABSTRACT
Hydrosoluble glycogen is the major energy storage compound in bacteria, archaea, fungi, and animal cells. In contrast, photosynthetic eukaryotes have evolved to build a highly organized semicrystalline granule of starch. Several enzymes are involved in polysaccharide synthesis, among which glycogen or starch synthase catalyze the elongation of the α-1,4-glucan chain. Ostreococcus tauri, accumulates a single starch granule and contains three starch synthase III (SSIII) isoforms, known as OsttaSSIII-A, OsttaSSIII-B and OsttaSSIII-C. After amino acids sequence analysis we found that OsttaSSIII-C lacks starch-binding domains, being 49% identical to the catalytic region of the SSIII from Arabidopsis thaliana and 32% identical to the entire Escherichia coli glycogen synthase. The recombinant, highly purified OsttaSSIII-C exhibited preference to use as a primer branched glycans (such as rabbit muscle glycogen and amylopectin), rather than amylose. Also, the enzyme displayed a high affinity toward ADP-glucose. We found a marked conservation of the amino acids located in the catalytic site, and specifically determined the role of residues R270, K275 and E352 by site-directed mutagenesis. Results show that these residues are important for OsttaSSIII-C activity, suggesting a strong similarity between the active site of the O. tauri SSIII-C isoform and other bacterial glycogen synthases.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Starch Synthase
/
Glycogen Synthase
/
Chlorophyta
/
Glycogen
Type of study:
Diagnostic_studies
Limits:
Animals
Language:
En
Journal:
Biochimie
Year:
2017
Document type:
Article
Affiliation country:
Argentina