Reaction: (1) 2 α-isomaltosyl-(1→4)-maltotriose = α-isomaltosyl-(1→3)-α-isomaltosyl-(1→4)-maltotriose + maltotriose
(2) α-isomaltosyl-(1→3)-α-isomaltosyl-(1→4)-maltotriose = cyclobis-(1→6)-α-nigerosyl + maltotriose
Systematic name: α-isomaltosyl-(1→3)-1,4-α-D-glucan:1,4-α-D-glucan 3-α-isomaltosyltransferase
Comments: The enzyme, found in bacteria that produce cyclobis-(1→6)-α-nigerosyl, acts on the products of EC 2.4.1.24, 1,4-α-glucan 6-α;-glucosyltransferase. It catalyses the α-(1→3) transfer of the isomaltosyl moiety of one substrate to another, resulting in α-isomaltosyl-(1→3)-α-isomaltosyl-α-(1→4)-glucan formation. In addition, the enzyme catalyses the intramolecular cyclization of the product, eventually generating cyclobis-(1→6)-α-nigerosyl.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Aga, H., Maruta, K., Yamamoto, T., Kubota, M., Fukuda, S., Kurimoto, M. and Tsujisaka, Y. Cloning and sequencing of the genes encoding cyclic tetrasaccharide-synthesizing enzymes from Bacillus globisporus C11. Biosci. Biotechnol. Biochem. 66 (2002) 1057-1068. [PMID: 12092816]
2. Nishimoto, T., Aga, H., Mukai, K., Hashimoto, T., Watanabe, H., Kubota, M., Fukuda, S., Kurimoto, M. and Tsujisaka, Y. Purification and characterization of glucosyltransferase and glucanotransferase involved in the production of cyclic tetrasaccharide in Bacillus globisporus C11. Biosci. Biotechnol. Biochem. 66 (2002) 1806-1818. [PMID: 12400677]
3. Kim, Y.K., Kitaoka, M., Hayashi, K., Kim, C.H. and Cote, G.L. A synergistic reaction mechanism of a cycloalternan-forming enzyme and a D-glucosyltransferase for the production of cycloalternan in Bacillus sp. NRRL B-21195. Carbohydr. Res. 338 (2003) 2213-2220. [PMID: 14553982]