Antibacterial non-glycosidase activity of invertebrate destabilase-lysozyme and of its helical amphipathic peptides

Background: Since bactericidal properties of some lysozymes are independent of their glycosidase activity, we have investigated this phenomenon for destabilase-lysozyme (DL) from medicinal leech (Hirudo medicinalis). Methods: Glycosidase activity was determined on Micrococcus luteus, non-enzymatic antibacterial activity of heat-treated DL and of synthetic peptides alpha 1, alpha 2 and alpha 3 (fragments of its primary structure) on M. luteus, Escherichia coli, Bacillus brevis and Streptomyces chrysomallus. Results: Glycosidase activity disappeared after the heating of native DL at 100 degrees C for 40 min. Antibacterial activity of heat-treated DL for M. luteus MDMSU128 and MDMSU140 expressed as minimal inhibitory concentration was 9.8(.)10(-8) and 12(.)10(-8) M, respectively, and to E. coli MDMSU52 11(.)10(-8) M. Antibacterial activity of synthetic peptide alpha 1 for M. luteus MDMSU128 and for E coli MDMSU52 was 8.3(.)10(-5) and 4.9(.)10(-5) M, respectively. Conclusion: DL is the first invertebrate lysozyme with combined enzymatic and non-enzymatic antibacterial action.