June 2008
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10 Reads
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4 Citations
SUMMARY –Lysozymes (mucopeptide N-acetylmuramylhydrolase, EC 3.2.1.17) isolated from human milk (HML) and bovine milk (BML) were subjected to -irradiation and their radiosensitivity was compared to that of egg white lysozyme (EWL). When irradiated in phosphate buffer, pH 6.2, the enzymes were fairly sensitive to -irradiation. Inactivation followed first order kinetics and depended upon protein concentration. BML was more radiosensitive than HML and EWL. Comparisons of the ultraviolet scans of the native and irradiated enzymes indicated that tryptophan was being destroyed in HML as it is known to occur in EWL. Hydroxy radical scavengers, cysteine and t-butanol, afforded radioprotective action for the milk lysozymes. In a dry state, both the milk lysozymes were less sensitive to -irradiation than in aqueous solution, requiring Mrad dosages for partial inactivation compared to Krad dosages for the same extent of inactivation in aqueous solution. However, as was observed in aqueous solution and also in the dry state, BML was more radiosensitive than HML and EWL.