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Protein dissimilation by human salivary-sediment bacteria
1Department of Preventive and Community Dentistry, University of Melbourne, Australia.
Journal of Dental Research
|February 1, 1989
Summary
Salivary sediment bacteria extensively hydrolyze unstructured proteins like caseins and histones. This process releases ammonia and amines, with putrescine production linked to arginine-rich histone breakdown.
Area of Science:
- Microbiology
- Biochemistry
- Oral Biology
Background:
- Salivary sediment harbors bacteria capable of protein hydrolysis.
- Understanding the substrate specificity and products of this hydrolysis is crucial for oral health research.
Purpose of the Study:
- To investigate the hydrolysis of various proteins by salivary sediment bacteria.
- To identify the specific protein structures susceptible to bacterial degradation.
- To characterize the byproducts of protein hydrolysis, including amines and ammonia.
Main Methods:
- Incubation of proteins with salivary sediment in a lactate-salt medium.
- Monitoring protein hydrolysis using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).
- Quantification of hydrogen ions (pH), amines (HPLC), and ammonia (glutamate dehydrogenase).
Main Results:
- Caseins (alpha s1, beta, kappa) and histones (H1, H3) were extensively hydrolyzed, attributed to their lack of tertiary structure.
- Putrescine was detected from arginine catabolism of histone H3; other proteins did not yield putrescine or cadaverine.
- Ammonium ion increase correlated with glutaminyl/asparaginyl residues, indicating bacterial deamidation.
Conclusions:
- Salivary sediment bacteria possess proteolytic activity targeting unstructured proteins.
- Bacterial deamination of glutamine and asparagine contributes to ammonia production.
- The proteolytic activity is distinct from trypsin-like enzymes.