Larval Tenebrio molitor (Coleoptera: Tenebrionidae) Fat Body Extracts Catalyze Firefly D-Luciferin- and ATP-Dependent Chemiluminescence: A Luciferase-like Enzyme*

Ultraweak light emission was detected upon injection of firefly luciferin into live Tenebrio larvae. A chemilumi-nescent enzymatic activity dependent on molecular oxygen, D-luciferin and MgATP was then isolated from larval fat body extracts by precipitation with 70% ammonium sulfate. D-Luciferin and ATP can be replaced by luciferyl-adenylate. Pyrophosphate is a main product from the chemiluminescent reaction. The in vitro chemiluminescence intensity was not affected by peroxidase inhibitors such as N₃^?_- (0.5 mM) and CN^? (1 mM), attesting to its nonperoxidatic nature but was strongly inhibited by AMP (1 mM), luciferin 6′-ethyl ether (1 mM) and sodium pyrophosphate (2 mM), well-known firefly lucifer-ase inhibitors. Some physical-chemical properties of this enzymatic activity were similar to those of firefly lucif-erase (K_MATP = 195 μM; K_0.5 luciferin - 0.8 mM; optimum pH 8.5; δ_max= 610 nm at pH 8.5; firefly lucifer-ase: δ_max= 565 nm at pH 8.0 and 619 mm at pH 6.0), but the chemiluminescence was not affected by addition of polyclonal antibodies raised against Photinus pyralis luciferase. These data suggest that this chemiluminescence results from a ligase with luciferase activity.