Lys-1 is a lysozyme encoded by the Caenorhabditis elegans lys-1 gene. This gene is one of a several lysozyme genes upregulated upon infection by the Gram-negative bacterial pathogen Serratia marcescens. Lys-1 contains a glycosyl hydrolase family 25 (GH25) catalytic domain. This family also includes Lys-5 from Caenorhabditis elegans.