In the firefly light organ, oxyluciferin, a product of the light-emitting reaction of firefly luciferase, is thought to be converted into luciferin. Previously, we isolated the luciferin-regenerating enzyme (LRE) from Photinus pyralis. LRE plays an important role in the recycling of oxyluciferin into luciferin. We have cloned two cDNAs encoding LRE, G-LRE and H-LRE, from poly(A)+ RNA of the lanterns of Luciola cruciata and Luciola lateralis, using reverse transcription-polymerase chain reaction, 5'-RACE (5'-rapid amplification of cDNA ends) and 3'-RACE. The putative translation products have molecular masses of 33,804 and 34,285 Da, corresponding to 309 and 307 amino acids, respectively. The deduced amino acid sequence of G-LRE shows 57 and 56% identity with H-LRE and A-LRE (P. pyralis), respectively. LRE (G-LRE, H-LRE, A-LRE) shows at most 39% amino acid sequence identity with insect anterior fat protein (AFP) and mammalian senescence marker protein-30 (SMP30). G-LRE and H-LRE were successfully expressed under the control of the lac promoter in Escherichia coli.