1q4n: Difference between revisions
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'''Structural studies of Phe256Trp of human salivary alpha-amylase: implications for the role of a conserved water molecule and its associated chain in enzyme activity''' | '''Structural studies of Phe256Trp of human salivary alpha-amylase: implications for the role of a conserved water molecule and its associated chain in enzyme activity''' | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Ramasubbu, N.]] | [[Category: Ramasubbu, N.]] | ||
[[Category: | [[Category: Amylase]] | ||
[[Category: | [[Category: Inhibitor]] | ||
[[Category: | [[Category: Mutagenesis]] | ||
[[Category: | [[Category: Tri]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 05:51:39 2008'' | |||
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Revision as of 02:51, 3 May 2008
Structural studies of Phe256Trp of human salivary alpha-amylase: implications for the role of a conserved water molecule and its associated chain in enzyme activity
Overview
In the mechanism of hydrolysis of starch by alpha-amylases, a conserved water molecule bridging two catalytic residues has been implicated. In human salivary alpha-amylase (HSAmy), this water (W641), observed in many alpha-amylase structures, is part of a chain of water molecules. To test the hypothesis that W641 may be involved in the mechanism, Phe256 in the close vicinity was mutated to a Trp residue. X-ray structure of F256W complexed to 2-amino-2-(hydroxyethyl)-1,3-propanediol at 2.1A revealed that the water chain is disrupted. In the F256W structure exhibits a positional shift in His305, characteristic of alpha-amylase complex structures. Kinetic analysis, in comparison with HSAmy, revealed that the mutant exhibited a 70-fold decrease in the specific activity for starch and significantly reduced k(cat) (20-fold) and K(m) (4-fold) for maltoheptaoside. Collectively, these results suggest that W641 and the chain of water molecules may be critical for the alpha-amylase activity.
About this Structure
1Q4N is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Structural studies of a Phe256Trp mutant of human salivary alpha-amylase: implications for the role of a conserved water molecule in enzyme activity., Ramasubbu N, Sundar K, Ragunath C, Rafi MM, Arch Biochem Biophys. 2004 Jan 1;421(1):115-24. PMID:14678792 Page seeded by OCA on Sat May 3 05:51:39 2008
