Lysozymes are hydrolytic enzymes characterized by their capacity to cleave the 1,4-β linkages between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, causing cellular lysis and, subsequently, the death of microorganisms. Hence, lysozymes represent an important component of defence in most insects. In this work, one lysozyme was purified from uninfected and uninjured Lonomia obliqua pupae, which indicates that it is produced constitutively. However, the expression of genes that produce the lysozyme in L. obliqua was seen to increase threefold after infection. The increase in the production of antimicrobial molecules after injuries and infections is a common feature in insects. By transcriptomic analysis, the complete amino acid sequence of this enzyme was determined, and it consisted of 139 amino acids, with molecular mass of 15.9 kDa and pI value of 8.82. Alignment and comparison with other lysozymes indicate that it has 83.7% sequence identity with the lysozyme from the moth Hyalophora cecropia and higher identity with C-type than I-type lysozymes. The possible structure was predicted and indicates the presence of α helix, 3₁₀ helix, β strand, (β) turn and other secondary structures. The description of a new lysozyme contributes to the overall knowledge of these important antimicrobial molecules.