Expression of angiotensin-converting enzyme-related carboxydipeptidases in the larvae of four species of fly.
HieACE, a soluble 70 kDa protein related to the angiotensin-converting enzyme (ACE) has recently been identified, characterized and cloned from the adult buffalo fly (Haematobia irritans exigua). HieACE is enzymatically similar to the mammalian ACEs and its predicted amino acid sequence has 42% identity with the mammalian testicular ACEs. In adult H.i. exigua, HieACE expression is restricted to the compound ganglion and posterior midgut, and the maturing male reproductive system. Western blot analysis was used to investigate the expression of HieACE and its homologues in the larvae of H.i. exigua, Drosophila melanogaster, the sheep blowfly (Lucilia cuprina), the Old World screwworm fly (Chrysomya bezziana) and a secondary strike fly, Chrysomya rufifacies. Dipteran ACE homologues of 65-70 kDa were detected in all the larval instars investigated. Most of the immunoreactive proteins were concentrated in the soluble fraction. The first and second larval instars of L. cuprina and C. bezziana appeared to express two ACE homologues. These larvae were also found to secrete (or excrete) the ACE homologue in larval cultures. The presence of ACE-like enzymes in these larvae was confirmed by the measurement of carboxydipeptidase activity that was inhibited by the specific ACE inhibitor, captopril. The tissue distributions of the ACE homologues in the third instar larvae of H.i. exigua and L. cuprina were examined. As in adult H.i. exigua, HieACE was detected in the larval ganglion, but in contrast to the restricted distribution in the adult stage midgut, HieACE was found throughout the digestive system, and in the salivary glands of H.i. exigua larvae. The expression pattern in the gut of L. cuprina larvae was similar despite the differences in diet and habitat. The most striking difference from the adult stage H.i. exigua was the expression of HieACE and its L. cuprina homologues in the hindgut and Malpighian tubules of these larvae. These results suggest that the role(s) played by the dipteran ACE-like enzymes differ between the adult and larval stages.
Wijffels
G
G
CSIRO Tropical Agriculture, Long Pocket Laboratories, Indooroopilly, Queensland, Australia. gene.wijffels@tag.csiro.au
Gough
J
J
Muharsini
S
S
Donaldson
A
A
Eisemann
C
C
D000818:Animals; D004175:Diptera / Q000201:enzymology*; D004331:Drosophila melanogaster / Q000201:enzymology; D007814:Larva / Q000201:enzymology; D009117:Muscidae / Q000201:enzymology; D007703:Peptidyl-Dipeptidase A / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
D007703:Peptidyl-Dipeptidase A