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| [[Image:1wpc.jpg|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1wpc| PDB=1wpc | SCENE= }} | | {{STRUCTURE_1wpc| PDB=1wpc | SCENE= }} |
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| '''Crystal structure of maltohexaose-producing amylase complexed with pseudo-maltononaose'''
| | ===Crystal structure of maltohexaose-producing amylase complexed with pseudo-maltononaose=== |
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| ==Overview==
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| Maltohexaose-producing amylase, called G6-amylase (EC 3.2.1.98), from alkalophilic Bacillus sp.707 predominantly produces maltohexaose (G6) from starch and related alpha-1,4-glucans. To elucidate the reaction mechanism of G6-amylase, the enzyme activities were evaluated and crystal structures were determined for the native enzyme and its complex with pseudo-maltononaose at 2.1 and 1.9 A resolutions, respectively. The optimal condition for starch-degrading reaction activity was found at 45 degrees C and pH 8.8, and the enzyme produced G6 in a yield of more than 30% of the total products from short-chain amylose (DP = 17). The crystal structures revealed that Asp236 is a nucleophilic catalyst and Glu266 is a proton donor/acceptor. Pseudo-maltononaose occupies subsites -6 to +3 and induces the conformational change of Glu266 and Asp333 to form a salt linkage with the N-glycosidic amino group and a hydrogen bond with secondary hydroxyl groups of the cyclitol residue bound to subsite -1, respectively. The indole moiety of Trp140 is stacked on the cyclitol and 4-amino-6-deoxyglucose residues located at subsites -6 and -5 within a 4 A distance. Such a face-to-face short contact may regulate the disposition of the glucosyl residue at subsite -6 and would govern the product specificity for G6 production.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15518553}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15518553 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15518553}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Alpha-amylase]] | | [[Category: Alpha-amylase]] |
| [[Category: Maltohexaose-producing amylase]] | | [[Category: Maltohexaose-producing amylase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 13:58:48 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 10:26:17 2008'' |
