angiotensinogen and pepstatin

Although renin was identified as playing a part in cardiovascular homeostasis by the experiments of Goldblatt in the 1930s, neither its physiological role in organs other than the kidney nor its contribution to the genesis of essential hypertension have been defined. It is difficult to interpret studies with converting enzyme inhibitors because of their multiple pharmacological effects. Specific inhibitors of renin appropriate for clinical investigation would help to resolve many questions. Four classes of compounds have been shown to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogues of angiotensinogens and peptides that are related to the amino-terminal sequence of prorenin. Of these, it is likely that angiotensinogen analogues will be the first applied in human studies. The minimal substrate for renin has the sequence: His-Pro-Phe-His-Leu-Val-Tyr. Variants of this sequence have yielded competitive inhibitors. Remarkably active compounds have recently been synthesized by reducing the peptide bond that is cleaved by renin, or by incorporating the amino acid statine, found in pepstatin. These compounds have been shown to be effective in dogs, rats and monkeys and, most recently, preliminary studies have reported their efficacy in man. Recent studies with one of these inhibitors, RIP, raise questions concerning both its specificity and site of action.

Topics: Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Animals; Antibodies, Monoclonal; Antihypertensive Agents; Blood Pressure; Heart Rate; Humans; Hypertension; Oligopeptides; Pepstatins; Renin

The important role of the renin-angiotensin system (RAS) in the maintenance of high blood pressure in certain forms of hypertension is well established. Inhibition of the RAS has therefore been studied with the aim to develop antihypertensive agents. Pharmacologic interferences with the RAS are possible at all steps of the formation, action and degradation of angiotensin II (ANG II). Renin activity can be inhibited by peptide analogues of angiotensinogen, peptides derived from the amino terminal sequence of pro-renin, inhibitors of acid proteases (pepstatin) and by specific renin antibodies. Inhibitors of the converting enzyme also prevent the formation of ANG II. ANG II receptor blockers (saralasin) prevent the action of the effector peptide of the RAS at the target cells. While some modes of intervention are still theoretical or experimental possibilities, others, e.g. inhibition of converting enzyme, are already used clinically for antihypertensive treatment.

Topics: Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Animals; Antibodies; Enzyme Precursors; Humans; Pepstatins; Renin; Renin-Angiotensin System

Topics: Amino Acid Sequence; Angiotensin I; Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Animals; Blood Pressure; Callithrix; Chemical Phenomena; Chemistry; Dogs; Horses; Humans; Macaca fascicularis; Oligopeptides; Papio; Pepstatins; Rats; Renin; Renin-Angiotensin System; Teprotide

Topics: Angiotensin II; Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Angiotensins; Animals; Blood Pressure; Blood Volume; Brain; Brain Chemistry; Captopril; Dogs; Enzyme Inhibitors; Homeostasis; Oligopeptides; Pepstatins; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Angiotensin; Renin; Renin-Angiotensin System; Saralasin; Teprotide

Three aspartic proteases (SVAPs) have been isolated from venom of the saw-scaled viper, Echis ocellatus. In confirmation of prior transcriptomic predictions, all three forms match to sequences of either of the two SVAP transcripts (EOC00051 and EOC00123), have a molecular weight of 42 kDa and possess a single N-glycan. The SVAPs act in a renin-like manner, specifically cleaving human and porcine angiotensinogen into angiotensin-1 and possess no general protease activity. Their activity is completely inhibited by the aspartyl protease inhibitor Pepstatin A.

Topics: Amino Acid Sequence; Angiotensin I; Angiotensinogen; Animals; Aspartic Acid Proteases; Humans; Isoenzymes; Pepstatins; Protease Inhibitors; Swine; Viper Venoms; Viperidae

H-189, a synthetic human renin inhibitor, and pepstatin A, a naturally occurring inhibitor of aspartic proteinases, have been co-crystallized with the fungal aspartic proteinase endothiapepsin (EC 3.4.23.6). H-189 [Pro-His-Pro-Phe-His-Sta-(statyl)-Val-Ile-His-Lys] is an analogue of human angiotensinogen. Pepstatin A [Iva(isovaleryl)-Val-Val-Sta-Ala-Sta] is a blocked pentapeptide which inhibits many aspartic proteinases. The structures of the complexes have been determined by X-ray diffraction and refined to crystallographic R-factors of 0.15 and 0.16 at resolutions of 0.18 nm (1.8 A) and 0.2 nm (2.0 A) respectively. H-189 is in an extended conformation, in which the statine residue is a dipeptide analogue of P1 and P'1 as indicated by the conformation and network of contacts and hydrogen bonds. Pepstatin A has an extended conformation to the P'2 alanine residue, but the leucyl side chain of the terminal statine residue binds back into the S'1 subsite, and an inverse gamma-turn occurs between P'1 and P'3. The hydroxy moiety of the statine at P1 in both complexes displaces the solvent molecule that hydrogen-bonds with the catalytic aspartate residues (32 and 215) in the native enzyme. Solvent molecules originally present in the native structure at the active site are displaced on inhibitor binding (12 when pepstatin A binds; 16 when H-189 binds).

Topics: Amino Acid Sequence; Angiotensinogen; Aspartic Acid Endopeptidases; Binding Sites; Humans; Models, Molecular; Molecular Sequence Data; Pepstatins; Protein Conformation; Renin; Thermodynamics; X-Ray Diffraction

1. We investigated the mechanism of tetradecapeptide-induced vasoconstriction by studying the metabolism of tetradecapeptide (TDP), angiotensinogen, and angiotensin I (AI) and angiotensin II (AII) by isolated perfused rat hindlimbs. 2. Using HPLC and specific RIAs we have quantified six angiotensin peptides: pentapeptide(4-8), hexapeptide(3-8), heptapeptide(2-8), octapeptide(1-8), nonapeptide(2-10) and decapeptide(1-10) in hindlimb effluent. 3. TDP-induced vasoconstriction was associated with generation of predominantly AI and AII, with smaller amounts of the other peptides measured. 4. Captopril prevented vasoconstriction and inhibited AII production by 80%, indicating a dominant role for AI generation in the vascular response to TDP. 5. Evidence that renin is not the enzyme responsible for AI generation from TDP includes: first, the failure of angiotensinogen to cause vasoconstriction or angiotensin peptide generation despite very high amounts of AI and AII generation from TDP; second, the resistance of the TDP-induced vasoconstriction and angiotensin peptide generation to inhibition by pepstatin; and third, the failure of bilateral nephrectomy 24 h before the experiment to influence the vascular and angiotensin peptide response to TDP. 6. AII was cleared with 41% efficiency, with generation of penta-, hexa-, and heptapeptides. 7. AI was cleared with 59% efficiency; this was reduced to 24% by captopril, indicating a conversion of at least 35% of AI to AII by ACE. 8. These studies have identified vascular metabolism of AI and AII to be an efficient process, with both ACE and aminopeptidases playing an important role, and indicate that those peptidases which cleave TDP to generate AI are unlikely to play any role in AI generation in vivo.

Topics: Angiotensin I; Angiotensin II; Angiotensinogen; Animals; Captopril; Cattle; Hindlimb; Kidney; Nephrectomy; Pepstatins; Perfusion; Rats; Renin; Vasoconstrictor Agents

The structure-conformation relationships of a series of angiotensinogen6-13 (ANG6-13, His-Pro-Phe-His-Leu-Val-Ile-His) congeners substituted by Nin-For-Trp (Ftr), D-Ftr or Trp at the N-terminus, Tyr at the C-terminus and Phe psi[CH2NH]Phe at the P1-P'1 cleavage site (i.e. Leu10-Val11) were studied using resonance energy transfer coupled with molecular modeling of the peptide conformation using macromolecular energy refinement and dynamics simulation. Average end-to-end intramolecular distances (r) of the peptides in solution were determined by fluorescence spectroscopy. For example, Ac-Ftr-Pro-Phe-His-Phe psi[CH2NH]Phe-Val-Tyr-NH2 (U-70714E) gave an average intramolecular donor (Tyr)-acceptor (Ftr) distance of 16.3A in aqueous solution. This experimental value was consistent with a distance of 17.9 A determined by molecular modeling of U-70714E to a human renin 3-D structure (developed from known homologous aspartyl protease inhibitor X-ray crystallographic data) followed by simulation of the solution phase conformation of the peptide. An extended backbone secondary structure of U-70714E is suggested from these studies and the relationship(s) of structure-conformation to structure-activity was explored by analysis of several congeners of U-70714E, a potent (IC50 = 3.0 X 10(-9)M) inhibitor of human renin in vitro.

Topics: Angiotensinogen; Energy Transfer; Humans; Models, Molecular; Oligopeptides; Pepstatins; Peptide Fragments; Peptides; Protein Conformation; Renin; Spectrometry, Fluorescence; Structure-Activity Relationship