The full-length intronless firefly luciferase gene and its deletion mutant which lacked 48 nucleotides from the initiation codon (ATG) were inserted into the high expression secretion vector. pIN-Ⅲ-ompA3. and introducedinto E. coli cells in which high level and no luciferase activity were detected, respectively.This result shows that the first sixteen N-terminal amino acids of firefly luciferase involve in catalytic activity.