Functional conservation of the active sites of human and Drosophila angiotensin I-converting enzyme

Human somatic angiotensin I-converting enzyme (sACE) has two active sites p resent in two homologous protein domains, resulting from a tandem gene dupl ication. It has been proposed that the N-and C-terminal active sites can ha ve specific in vivo roles. In Drosophila melanogaster, Ance and Acer code f or two ACE-like single-domain proteins, also predicted to have distinct phy siological roles. We have investigated the relationship of Ance and Acer to the N- and C-domains of human sACE by genomic sequence analysis and by usi ng domain-selective inhibitors, including RXP 407, a selective inhibitor of the human N-domain. These phosphinic peptides were potent inhibitors of Ac er. but not of Ance, We conclude that the active sites of the N-domain and of Acer share structural features that permit the binding of the unusual RX P307 inhibitor and the hydrolysis of a broader range of peptide structures. In comparison, Ance, like the human C-domain of ACE, displays greater inhi bitor selectivity. From the analysis of the published sequence of the Adh r egion of Drosophila chromosome 2, which carries Ance, Acer, and four additi onal ACE-like genes, we also suggest that this functional conservation is r eflected in an ancestral gene structure identifiable in both protostome and deuterostome lineages and that the duplication seen in vertebrate genomes predates the divergence of these lineages. The conservation of ACE enzymes with distinct active sites in the evolution of both vertebrate and inverteb rate species provides further evidence that these two kinds of active sites have different physiological functions.