TY - JOUR
T1 - Structure of human salivary α-amylase at 1.6 Å resolution
T2 - Implications for its role in the oral cavity
AU - Ramasubbu, Narayanan
AU - Paloth, Venugopalan
AU - Luo, Yaoguang
AU - Brayer, Gary D.
AU - Levine, Michael J.
PY - 1996/5/1
Y1 - 1996/5/1
N2 - Salivary α-amylase, a major component of human saliva, plays a role in the initial digestion of starch and may be involved in the colonization of bacteria involved in early dental plaque formation. The three-dimensional atomic structure of salivary amylase has been determined to understand the structure-function relationships of this enzyme. This structure was refined to an R value of 18.4% with 496 amino-acid residues, one calcium ion, one chloride ion and 170 water molecules. Salivary amylase folds into a multidomain structure consisting of three domains, A, B and C. Domain A has a (β/α)8-barrel structure, domain B has no definite topology and domain C has a Greek-key barrel structure. The Ca2+ ion is bound to Asn100, Arg158, Asp167, His201 and three water molecules. The Cl- ion is bound to Arg195, Asn298 and Arg337 and one water molecule. The highly mobile glycine-rich loop 304-310 may act as a gateway for substrate binding and be involved in a 'trap-release' mechanism in the hydrolysis of substrates. Strategic placement of calcium and chloride ions, as well as histidine and tryptophan residues may play a role in differentiating between the glycone and aglycone ends of the polysaccharide substrates. Salivary amylase also possesses a suitable site for binding to enamel surfaces and provides potential sites for the binding of bacterial adhesins.
AB - Salivary α-amylase, a major component of human saliva, plays a role in the initial digestion of starch and may be involved in the colonization of bacteria involved in early dental plaque formation. The three-dimensional atomic structure of salivary amylase has been determined to understand the structure-function relationships of this enzyme. This structure was refined to an R value of 18.4% with 496 amino-acid residues, one calcium ion, one chloride ion and 170 water molecules. Salivary amylase folds into a multidomain structure consisting of three domains, A, B and C. Domain A has a (β/α)8-barrel structure, domain B has no definite topology and domain C has a Greek-key barrel structure. The Ca2+ ion is bound to Asn100, Arg158, Asp167, His201 and three water molecules. The Cl- ion is bound to Arg195, Asn298 and Arg337 and one water molecule. The highly mobile glycine-rich loop 304-310 may act as a gateway for substrate binding and be involved in a 'trap-release' mechanism in the hydrolysis of substrates. Strategic placement of calcium and chloride ions, as well as histidine and tryptophan residues may play a role in differentiating between the glycone and aglycone ends of the polysaccharide substrates. Salivary amylase also possesses a suitable site for binding to enamel surfaces and provides potential sites for the binding of bacterial adhesins.
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U2 - https://doi.org/10.1107/S0907444995014119
DO - https://doi.org/10.1107/S0907444995014119
M3 - Article
C2 - 15299664
VL - 52
SP - 435
EP - 446
JO - Acta Crystallographica - Section D Biological Crystallography
JF - Acta Crystallographica - Section D Biological Crystallography
SN - 0907-4449
IS - 3
ER -