A gut-specific serine protease from the malaria vector Anopheles gambiae is downregulated after blood ingestion

A chymotrypsin-like serine protease gene (AgChyL) was cloned from the mosqu ito Anopheles gambiae by a polymerase chain reaction (PCR)-based subtractiv e cDNA cloning strategy. AgChyL messenger RNA (mRNA) is abundant in the adu lt female gut prior to, and for 8 h following, a blood meal. During the pea k of digestion, from 12 to 24 h following a blood meal, AgChyL mRNA abundan ce decreased to barely detectable levels. AgChyL mRNA was abundant again by 48 h following a blood meal. Recombinant pro-AgChyL was expressed in Esche richia coli. The pro-enzyme can be activated by trypsin. Activated AgChyL c leaves the synthetic chymotrypsin substrate succinyl-L-Ala-Ala-Pro-Phe-nitr oanilide, but not two other synthetic chymotrypsin substrates or synthetic trypsin and elastase substrates. The potential role of AgChyL in the coordi nation of An. gambiae digestion is discussed.