Structure of Human Salivary α-Amylase at 1.6 Å Resolution: Implications for its Role in the Oral Cavity
Acta Crystallographica Section D
Volume 52, Issue 3, pages 435–446, May 1996
How to Cite
Ramasubbu, N., Paloth, V., Luo, Y., Brayer, G. D. and Levine, M. J. (1996), Structure of Human Salivary α-Amylase at 1.6 Å Resolution: Implications for its Role in the Oral Cavity. Acta Crystallographica Section D, 52: 435–446. doi: 10.1107/S0907444995014119
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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 Asnl00, 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.