CHARACTERIZATION OF A NOVEL GUT-SPECIFIC CHITINASE GENE FROM THE HUMAN MALARIA VECTOR ANOPHELES-GAMBIAE

Chitinases that function in the molting of the larval exoskeleton have been characterized previously, However, chitinase expression in an ad ult insect gut has not been described. Here we report on the initial c haracterization and cloning of a novel chitinase gene that is expresse d specifically in the midgut of adult Anopheles gambiae females, Upon feeding, chitinase is secreted into the gut lumen as an inactive pro e nzyme that is later activated by trypsin. Thus, temporal regulation of chitinase activity is tightly coupled to the temporal pattern of tryp sin secretion, The enzyme may play a role in structuring the chitin-co ntaining extracellular peritrophic matrix, whose formation is also ind uced by feeding, A chitinase cDNA was cloned from a library enriched f or gut-specific sequences, The open reading frame encodes a 525-amino acid protein comprised of a putative catalytic domain at the N terminu s, a putative chitin-binding domain at the C terminus, and a threonine /serine/proline-rich amino acid stretch in between them, Northern anal ysis indicates that this chitinase is expressed exclusively in the gut s of adult females and not in adult carcasses or in any larval or pupa l tissues, The present findings suggest the possibility of using this chitinase as an antigen for a malaria transmission-blocking vaccine.