Role of Trp140 at subsite -6 on the maltohexaose production of maltohexaose-producing amylase from alkalophilic Bacillus sp.707Kanai, R., Haga, K., Akiba, T., Yamane, K., Harata, K.
(2006) Protein Sci. 15: 468-477
- PubMed: 16452622
- DOI: 10.1110/ps.051877006
- Primary Citation of Related Structures:
- PubMed Abstract:
- Biochemical and crystallographic analyses of maltohexaose-producing amylase from alkalophilic Bacillus sp. 707
Kanai, R.,Haga, K.,Akiba, T.,Yamane, K.,Harata, K.
(2004) Biochemistry 43: 14047
Maltohexaose-producing amylase (G6-amylase) from alkalophilic Bacillus sp.707 predominantly produces maltohexaose (G6) in the yield of >30% of the total products from short-chain amylose (DP=17). Our previous crystallographic study showed that G6-amy ...
Maltohexaose-producing amylase (G6-amylase) from alkalophilic Bacillus sp.707 predominantly produces maltohexaose (G6) in the yield of >30% of the total products from short-chain amylose (DP=17). Our previous crystallographic study showed that G6-amylase has nine subsites, from -6 to +3, and pointed out the importance of the indole moiety of Trp140 in G6 production. G6-amylase has very low levels of hydrolytic activities for oligosaccharides shorter than maltoheptaose. To elucidate the mechanism underlying G6 production, we determined the crystal structures of the G6-amylase complexes with G6 and maltopentaose (G5). In the active site of the G6-amylase/G5 complex, G5 is bound to subsites -6 to -2, while G1 and G6 are found at subsites +2 and -7 to -2, respectively, in the G6-amylase/G6 complex. In both structures, the glucosyl residue located at subsite -6 is stacked to the indole moiety of Trp140 within a distance of 4A. The measurement of the activities of the mutant enzymes when Trp140 was replaced by leucine (W140L) or by tyrosine (W140Y) showed that the G6 production from short-chain amylose by W140L is lower than that by W140Y or wild-type enzyme. The face-to-face short contact between Trp140 and substrate sugars is suggested to regulate the disposition of the glucosyl residue at subsite -6 and to govern product specificity for G6 production.
Biological Information Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.