Proteolytic sensitivity of the α subunit in luciferases ofPhotobacterium species

Bacterial luciferases isolated from strains of three species ofPhotobacterium (P. leiognathi, P. phosphoreum andP. fischeri) have been found to be considerably more sensitive to trypsin inactivation than luciferase fromBeneckea harveyi. P. leiognathi luciferase has a pseudo-first-order rate constant of inactivation of 0.14 min⁻¹ when exposed to 1 μg/ml (42 nM) trypsin. As judged by sodium dodecyl sulfate electrophoresis of the products of proteolysis, only the α subunit of the αβ heterodimeric luciferases ofPhotobacterium species was attacked by trypsin. After treatment of these enzymes with trypsin, the β subunit of eachPhotobacterium species retained its ability to reform active luciferase when renatured with native complementary α subunit.