Isolation of a trypsin‐like serine protease gene family from the sheep blowfly Lucilia cuprina

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Abstract
Various protease inhibitors active against both trypsin‐ and chymotrypsin‐like serine proteases were used to characterize gut proteases from Lucilia cuprina by in vitro feeding assays. Significant larval growth retardation was observed on feeding first‐instar larvae with trypsin inhibitors, particularly soybean trypsin inhibitor. Feeding of chymostatin, a specific chymotrypsin inhibitor, resulted in no significant growth retardation. This information suggests that trypsin‐like serine proteases are probably the major gut digestive enzymes. A DNA fragment obtained by PCR which coded for part of a putative trypsin gene from L. cuprina was used to isolate a four‐member multigene family of trypsins. The full nucleotide sequence of one of the genes and partial sequence from the other three genes were determined. Transcription of at least one of the genes has been confirmed. All four of the genes appear to have arisen by two separate gene duplication events.