The effect of some proteolytic enzymes on human salivary micelle-like structures

Abstract

Recent studies have demonstrated the presence of negatively charged, globular or micelle-like structures in human saliva. Photon correlation spectroscopy (PCS) has demonstrated these structures in parotid saliva to be initially 100–150 nm in diameter, increasing to about 450 nm 50 min after sampling. The newly formed acquired-enamel pellicle appears to consist mainly of such globular structures. Previously, it has been shown that pellicle proteins may be degraded by proteolytic activity, and furthermore, the proline-rich proteins adsorbed to hydroxyapatite may be degraded by proteolytic activity isolated from salivary sediments. The aim of this in vitro study was to determine the effect of some model enzymes on the salivary micelle-like structures (SMS). The integrity of the SMS was examined by PCS prior to and following addition of trypsin, pronase E and rennin to samples of freshly collected human parotid saliva. Trypsin caused a sudden reduction in both mean particle hydrodynamic diameter and PCS intensity. Pronase E had a similar though less pronounced effect, whereas rennin appeared to have little or no effect on the salivary micelle-like structures. Zeta-potential determinations indicated that trypsin-treated SMS had a slightly smaller net negative surface potential than untreated SMS, whereas pronase E resulted in a more negative surface potential, and rennin had no effect. This study indicates that the SMS are susceptible to specific enzymatic activity which may interfere with their assumed protective role in oral physiology.