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 22.214.171.124, glycogen(starch) synthase and EC 126.96.36.199, 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  or pollen .
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9031-53-2
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