Functional analysis of two invertebrate-type lysozymes from red swamp crayfish, Procambarus clarkii

Lysozyme is an important immune effector and is widely distributed in many organisms. In the present study, two novel invertebrate-type lysozymes (Pclysi1 and Pclysi2) were cloned from red swamp crayfish, Procambarus clarkii. Alignment analysis showed that these two genes were different in catalytic residues. Results of RT-PCR showed that these two genes share similar tissue distribution patterns, and both were upregulated after bacteria challenge. The mature recombinant proteins were expressed in Escherichia coli system and purified. Activity analysis revealed that rPclysi1 had no muramidase activity and isopeptidase activity, but had antimicrobial activity. Meanwhile, rPclysi2 was muramidase-deficient and had no antimicrobial activity, but possessed isopeptidase activity. Above data suggest that Pclysi1 and 2 may offer different functions in the crayfish immunity.