A COMPARISON OF THE LEECH THEROMYZON TESSULATUM ANGIOTENSIN I-LIKE MOLECULE WITH FORMS OF VERTEBRATE ANGIOTENSINOGENS - A HORMONAL SYSTEM CONSERVED IN THE COURSE OF EVOLUTION

After five steps of purification including gel permeation, anti-angiot ensin I affinity column chromatography followed by reverse-phase HPLC, a peptide immunoreactive to two different antisera (anti-angiotensin II and anti-angiotensin I) was purified to homogeneity from extracts o f the leech Theromyzon tessulatum. The first 14 amino acid residues of the purified peptide (DRVYIHPFHLLXWG) established by automated Edman degradation, reveal the existence in leeches of an angiotensin I-like molecule close to human angiotensin I. The sequence of the purified pe ptide presents 78.5% of homology with the N-terminal part of human ang iotensinogen. Moreover, in its sequence, this peptide presents the cle avage sites of vertebrate angiotensin metabolic enzymes, i.e. the reni n and the angiotensin-converting enzyme. This finding constitutes the first biochemical characterization of an angiotensin I in Invertebrate s. It also reflects the high conservation of angiotensins in the cours e of evolution, suggesting a fundamental role of this family in fluid homeostasis.