Purification and molecular cloning of c-type lysozyme from the common cutworm, Spodoptera litura

We have purified and characterized a new insect C-type lysozyme from the common cutworm, Spodoptera litura. Spodoptera lysozyme has been isolated by heat treatment, cation exchange, and reversed-phase chromatography from immunized hemolymph. The estimated molecular weight of the purified S. litura lysozyme is about 15 kDa. The isolated cDNA consists of 1039 bp with a 426 bp open reading frame, which encodes 142-amino acid residue polypeptide. The theoretical isoelectric point and molecular weight of mature Spodoptera lysozyme is 9.05 and 13964.8 Da, respectively. The deduced amino acid sequence of Spodoptera lysozyme shows the highest similarity (96.7%) with Spodoptera exigua among other lepidopteran species. Comparisons with other C-type lysozymes from invertebrates and vertebrates, Glu32 and Asp50 are responsible for the catalytic activity and eight cysteine residues are completely conserved in the same position as that of other lepidopteran lysozymes.