Automated Determination of Lysozyme

Lysozyme (EC 3.2.1.17; muramidase) is an enzyme of low relative molecular mass (Mr 14 500) that is widely distrib-uted in body tissues and secretions (1). The enzyme is normally present in plasma and in trace amounts in urine (2). High concentrations of lysozyme are found in leuko-cytes, neutrophilic granulocytes and monocytes, and mac-rophages; little, if any, is in lymphocytes (3). Clinical interest in lysozyme activity measurements has focused on leukemias, renal diseases, and meningitis (2-4). More recently, the lysozyme concentration of pleural fluid as well as the ratio of pleural lysozyme to serum lysozyme has been useful in diagnoses based on analysis of pleural effusions (5, 6). The most widely used assays for determining lysozyme are the turbidimetric kinetic (3, 7) and Lysoplate method