ROLE OF THE C-TERMINAL DOMAIN OF THE LYSOZYME OF CLOSTRIDIUM-ACETOBUTYLICUM ATCC-824 IN A CHIMERIC PNEUMOCOCCAL-CLOSTRIDIAL CELL-WALL LYTICENZYME

An active chimeric cell wall lytic enzyme has been constructed by doma in substitution between the major autolysins of Clostridium acetobutyl icum ATCC 824 and Streptococcus pneumoniae. The chimeric enzyme, built up by the fusion of the N-terminal domain of the pneumococcal LYTA am idase and the C-terminal domain of the clostridial LYC lysozyme, exhib ited an amidase activity capable of hydrolyzing choline-containing clo stridial cell walls with an efficiency 250-times higher than when test ed on pneumococcal cell walls. This experimental approach demonstrates the basic role of the C-terminal domain of the LYC lysozyme in substr ate recognition and provides additional support to our hypothesis of m odular evolution of these lytic enzymes. Moreover, the construction de scribed here confirmed the role of the C-terminal domains of the modul ar cell wall lytic enzymes on the optimal pH for catalytic activity. T o our knowledge, this is the first example of the construction of an a ctive chimeric lytic enzyme by fusing genes that lack nucleotide homol ogy and are derived from different bacterial genera.