|
|
| Line 1: |
Line 1: |
| [[Image:1v3i.jpg|left|200px]] | | {{Seed}} |
| | [[Image:1v3i.png|left|200px]] |
|
| |
|
| <!-- | | <!-- |
| Line 9: |
Line 10: |
| {{STRUCTURE_1v3i| PDB=1v3i | SCENE= }} | | {{STRUCTURE_1v3i| PDB=1v3i | SCENE= }} |
|
| |
|
| '''The roles of Glu186 and Glu380 in the catalytic reaction of soybean beta-amylase'''
| | ===The roles of Glu186 and Glu380 in the catalytic reaction of soybean beta-amylase=== |
|
| |
|
|
| |
|
| ==Overview==
| | <!-- |
| It has previously been suggested that the glutamic acid residues Glu186 and Glu380 of soybean beta-amylase play critical roles as a general acid and a general base catalyst, respectively. In order to confirm the roles of Glu186 and Glu380, each residue was mutated to a glutamine residue and the crystal structures of the substrate (E186Q/maltopentaose) and product (E380Q/maltose) complexes were determined at resolutions of 1.6 Angstrom and 1.9 Angstrom, respectively. Both mutant enzymes exhibited 16,000- and 37,000-fold decreased activity relative to that of the wild-type enzyme. The crystal structure of the E186Q/maltopentaose complex revealed an unambiguous five-glucose unit at subsites -2 to +3. Two maltose molecules bind on subsites -2 to -1 and +2 to +3 in the E380Q/maltose complex, whereas they bind in tandem to -2 to -1 and +1 to +2 in the wild-type/maltose complex. The conformation of the glucose residue at subsite -1 was identified as a stable (4)C(1) alpha-anomer in the E380Q/maltose complex, whereas a distorted ring conformation was observed in the wild-type/maltose complex. The side-chain movement of Gln380 to the position of a putative attacking water molecule seen in the wild-type enzyme caused the inactivation of the E380Q mutant and an altered binding pattern of maltose molecules. These results confirm the critical roles played by Glu186 in the donation of a proton to the glycosidic oxygen of the substrate, and by Glu380 in the activation of an attacking water molecule. The observed difference between the backbones of E186Q/maltopentaose and E380Q/maltose in terms of Thr342 suggests that the side-chain of Thr342 may stabilize the deprotonated form of Glu186 after the cleavage of the glycosidic bond.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15178253}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15178253 is the PubMed ID number. |
| | --> |
| | {{ABSTRACT_PUBMED_15178253}} |
|
| |
|
| ==About this Structure== | | ==About this Structure== |
| Line 27: |
Line 31: |
| [[Category: Mikami, B.]] | | [[Category: Mikami, B.]] |
| [[Category: Utsumi, S.]] | | [[Category: Utsumi, S.]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 12:01:56 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 12:14:19 2008'' |