Lysozyme activity in the initially formed in situ pellicle

Lysozyme is one of the most abundant enzymatic components in the salivary pellicle. The purpose of the present in situ study was to determine if and to which extent lysozyme immobilised in pellicles exposes enzymatic activity. Influence of different oral sites and pellicle formation time on enzyme activity was also evaluated. Bovine enamel stabs (5 mm diameter) were fixed on buccal and oral sites of individual trays worn by six subjects for 3 and 30 min on different days. After pellicle formation, stabs were removed from the trays and rinsed with running water. Afterwards, pellicle-bound lysozyme activity was determined via lysis of Micrococcus lysodeicticus photometrically in two steps. In a first step, lysozyme was desorbed in phosphate buffer and dissolved activity was measured. In a second step, stabs were incubated in phosphate buffer with the substrate and remaining immobilised activity was determined. All investigated pellicles exhibited lysozyme activity. Great intra- and inter-individual differences were observed. Mean desorbed activity of 3 min-pellicles amounted to 26.06 +/- 17.81 U/cm(2) (30 min; 26.79 +/- 17.48). The remaining immobilised activity was 13.54 +/- 11.42 for 3 min-pellicles and 16.08 +/- 12.81 for 30 min-pellicles. Pellicle derived lysozyme showed a Michaelis type kinetic. Conclusion: In situ pellicle exposes lysozyme activity even after a 3 min formation period. Exposed enzyme activity is neither influenced by pellicle formation time nor by the site of pellicle formation. It shows great inter- and intra-individual differences. (c) 2005 Elsevier Ltd. All rights reserved.