Reaction: NDP-glucose + (1,4-α-D-glucosyl)n = NDP + (1,4-α-D-glucosyl)n+1
Other name(s): granule-bound starch synthase; starch synthase II (ambiguous); waxy protein; starch granule-bound nucleoside diphosphate glucose-starch glucosyltransferase; granule-bound starch synthase I; GBSSI; granule-bound starch synthase II; GBSSII; GBSS; NDPglucose-starch glucosyltransferase
Systematic name: NDP-glucose:1,4-α-D-glucan 4-α-D-glucosyltransferase
Comments: Unlike EC 2.4.1.11, glycogen(starch) synthase and EC 2.4.1.21, starch synthase, which use UDP-glucose and ADP-glucose, respectively, this enzyme can use either UDP- or ADP-glucose. Mutants that lack the Wx (waxy) allele cannot produce this enzyme, which plays an important role in the normal synthesis of amylose. In such mutants, only amylopectin is produced in the endosperm [3] or pollen [5].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9031-53-2
References:
1. Tsai, C.-Y. The function of the waxy locus in starch synthesis in maize endosperm. Biochem. Genet. 11 (1974) 83-96. [PMID: 4824506]
2. Nakamura, T., Vrinten, P., Hayakawa, K. and Ikeda, J. Characterization of a granule-bound starch synthase isoform found in the pericarp of wheat. Plant Physiol. 118 (1998) 451-459. [PMID: 9765530]
3. Fujita, N. and Taira, T. A 56-kDa protein is a novel granule-bound starch synthase existing in the pericarps, aleurone layers, and embryos of immature seed in diploid wheat (Triticum monococcum L.). Planta 207 (1998) 125-132. [PMID: 9951718]
4. Murai, J., Taira, T. and Ohta, D. Isolation and characterization of the three Waxy genes encoding the granule-bound starch synthase in hexaploid wheat. Gene 234 (1999) 71-79. [PMID: 10393240]
5. Nelson, O.E. The waxy locus in maize. II The location of the controlling element alleles. Genetics 60 (1968) 507-524.