Structural relationship between the enzymatic and streptococcal binding sites of human salivary α-amylase

F. A. Scannapicco, K. Bhandary, N. Ramasubbu, M. J. Levine

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Previous studies have demonstrated that human salivary α-amylase specifically binds to the oral bacterium Streptococcus gordonii. This interaction is inhibited by substrates such as starch and maltotriose suggesting that bacterial binding may involve the enzymatic site of amylase. Experiments were performed to determine if amylase bound to the bacterial surface possessed enzymatic activity. It was found that over one-half of the bound amylase was enzymatically active. In addition, bacterial-bound amylase hydrolyzed starch to glucose which was then metabolized to lactic acid by the bacteria. In further studies, the role of amylase's histidine residues in streptococcal binding and enzymatic function was assessed after their selective modification with diethyl pyrocarbonate. DEP-modified amylase showed a marked reduction in both enzymatic and streptococcal binding activities. These effects were diminished when DEP modification occurred in the presence of maltotriose. DEP-modified amylase had a significantly altered secondary structure when compared with native enzyme or amylase modified in the presence of maltotriose. Collectively, these results suggest that human salivary α-amylase may possess multiple sites for bacterial binding and enzymatic activity which share structural similarities.

Original languageEnglish (US)
Pages (from-to)1109-1115
Number of pages7
JournalBiochemical and Biophysical Research Communications
Issue number3
StatePublished - Dec 31 1990
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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