muramidase and cupric-chloride

The mechanism of irreversible inactivation of lysozyme at neutral pH at 100 degrees C, and effects of additives on the inactivation were investigated. The thermoinactivation of lysozyme at neutral pH was caused by intra- and intermolecular disulfide exchange and the production of irreversibly denatured lysozyme, which was destabilized by multiple chemical reactions other than disulfide exchange. In addition, independently, deamidation slightly affected the inactivation by causing a decrease of electrostatic interaction between positive charges of lysozyme and negative charges of the bacterial cell wall. As for the effects of additives on the inactivation, a small amount of copper ion suppressed intra- and intermolecular disulfide exchange by catalyzing air oxidation of heat-induced trace amounts of free thiols, and organic reagents (acetamide, ethanol, and glycerol) changed the mechanism of the inactivation to that under acidic conditions by shifting the pKa values of dissociable residues and also suppressed intermolecular disulfide exchange by decreasing hydrophobic interactions.

Topics: Acetamides; Animals; Chickens; Copper; Disulfides; Ethanol; Female; Glycerol; Hot Temperature; Hydrogen-Ion Concentration; Kinetics; Micrococcus luteus; Muramidase; Sulfhydryl Compounds; Thermodynamics

Groups of rabbits were exposed to chlorides of nickel, cadmium, copper, and cobalt at concentrations ranging from 0.2 to 0.6 mg/m3 (as metal) for 4-6 weeks (5 days/week, 6 hr/day). Activity of lysozyme (muramidase) in lavage fluid, in alveolar macrophages, and in culture medium from macrophages incubated at 37 degrees C for 1 and 20 hr was estimated using the lyso-plate technique, agar plates with heat-killed Micrococcus lysodeikticus. In the nickel-exposed rabbits lysozyme activity in the mucous membrane from the left main bronchus was also estimated. Following nickel exposure the lysozyme level was significantly decreased in lavage fluid, macrophages, and in culture medium from incubated macrophages but remained unchanged in the mucous membrane. After exposure to cadmium, copper, and cobalt, lysozyme levels increased or were unchanged.

Topics: Animals; Cadmium; Cadmium Chloride; Cobalt; Copper; Lung; Macrophages; Male; Mucous Membrane; Muramidase; Nickel; Rabbits