Molecular and functional characterization of an acetyl-CoA acetyltransferase from the adzuki bean borer moth Ostrinia scapulalis (Lepidoptera: Crambidae)

Two types of thiolases are involved in the synthesis and catabolism of fatty acids; acetyl-CoA acetyltransferase (AT) which catalyzes the formation of acetoacetyl-CoA from acetyl-CoA by transferring an acetyl group from one acetyl-CoA molecule to another, and 3-ketoacyl-CoA thiolase which catalyzes a reversible thiolytic cleavage of 3-ketoacyl-CoA into acetyl-CoA and acyl-CoA. Although many mammalian thiolases have been characterized in detail, no thiolases from insects have been functionally characterized to date. Here we report first characterization of an insect AT gene, Osat1, from the pheromone gland of the adzuki bean borer moth Ostrinia scapulalis (Lepidoptera; Crambidae). Osat1 encodes a 41.2 kDa protein comprising 396 amino acid residues (OsAT1), which possesses structural features of the thiolase family. An Osat1 homologue of Bombyx mori (Bmat1) was cloned through exploration of an EST library of the silkworm. Subsequent survey of the genome database revealed that B. mori has at least six Osat1 homologues, among which Bmat1 was most closely related to Osat1. We expressed recombinant OsAT1 using a baculovirus expression system, and verified that OsAT1 catalyzes the formation of acetoacetyl-CoA from acetyl-CoA. Osat1 was expressed in all adult tissues examined. These results indicate that OsAT1 is a functional AT ubiquitously expressed in O. scapulalis tissues.