A new aminopeptidase from diamondback moth provides evidence for a gene duplication event in Lepidoptera

We screened a midgut cDNA library from diamondback moth, Plutella xylostella, with a probe generated using sequence information from an aminopeptidase N gene from Manduca sexta (MsAPN-1). The sequence recovered (PxAPN-A) encodes a protein of 988 resides with a 60% sequence identity to MsAPN-1. The two proteins share a signal peptide which directs processing by the endoplasmic reticulum, a C-terminal hydrophobic region satisfying the criterion for a GPI anchor and cleavage, and the possibility of an O-glycosylated rigid stalk attached to the GPI anchor. PxAPN-A is more closely related to MsAPN-1 than it is to another aminopeptidase recently reported from P. xylostella. Sequence comparisons with other species suggests that at least one aminopeptidase gene duplication occurred in an ancestral lepidopteran.