1Q4N

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

1Q4N の概要

• エントリーDOI: 10.2210/pdb1q4n/pdb
• 分子名称: Alpha-amylase, salivary, CALCIUM ION, CHLORIDE ION, ... (5 entities in total)
• 機能のキーワード: amylase, mutagenesis, tris, inhibitor, hydrolase
• 由来する生物種: Homo sapiens (human)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 56233.04

構造登録者

Ramasubbu, N. (登録日: 2003-08-04, 公開日: 2004-03-16, 最終更新日: 2024-11-06)

主引用文献

Ramasubbu, N.,Sundar, K.,Ragunath, C.,Rafi, M.M.
Structural studies of a Phe256Trp mutant of human salivary alpha-amylase: implications for the role of a conserved water molecule in enzyme activity
Arch.Biochem.Biophys., 421:115-124, 2004

PubMed Abstract: 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.

PubMed: 14678792
DOI: 10.1016/j.abb.2003.10.007

実験手法

X-RAY DIFFRACTION (2.07 Å)