CLONING AND EXPRESSION OF AN EVOLUTIONARY CONSERVED SINGLE-DOMAIN ANGIOTENSIN-CONVERTING ENZYME FROM DROSOPHILA-MELANOGASTER

Mammalian somatic angiotensin converting enzyme (EC 3.4.15.1, ACE) con sists of two highly homologous (N- and C-) domains encoded by a duplic ated gene. We have identified an apparent single-domain (67 kDa) insec t angiotensin converting enzyme (AnCE) in embryos of Drosophila melano gaster which converts angiotensin I to angiotensin II (K-m, 365 mu M), removes Phe-Arg from the C terminus of bradykinin (K-m, 22 mu M), and is inhibited by ACE inhibitors, captopril (IC50 = 1.1 x 10(-9) M) and trandolaprilat (IC50 = 1.6 x 10(-8) M). We also report the cloning an d expression of a Drosophila AnCE cDNA which codes for a single-domain 615-amino acid protein with a predicted 17-amino acid signal peptide and regions with high levels of homology to both the N- and C-domains of mammalian somatic ACE, especially around the active site consensus sequence. Northern analysis identified a single 2.1-kilobase mRNA in D rosophila embryos, and Southern analysis of Drosophila genomic DNA ind icates that the insect gene is not duplicated. When expressed in COS-7 cells, the AnCE protein is a secreted enzyme, which converts angioten sin I to angiotensin II and is inhibited by captopril (IC50 = 5.6 x 10 (-9) M) and trandolaprilat (IC50 = 2 x 10(-8) M). The evolutionary sig nificance of these results is discussed.