Turbidimetric determination of lysozyme with Micrococcus lysodeikticus cells: reexamination of reaction conditions.

Factors affecting the activity of human lysozyme (EC 3.2.1.17) toward cell suspensions of Micrococcus lysodeikticus were reexamined. Effects of substrate concentration, pH, and ionic strength and matrix effects of protein were assessed with special emphasis on the interdependence of various parameters. On the basis of these evaluations, an optimized kinetic turbidimetric method for lysozyme assay was set up. The method was applied for automation with a System Olli 3000 analyzer. The new automated lysozyme assay proved good for routine clinical use in regard to analysis speed, sensitivity, linearity, and reproducibility. Reference values for serum, urinary, and cerebrospinal fluid lysozyme were assessed with the automated method.