ABSTRACT
Design modifications to the lead HIV-PR inhibitor 1 (MDL 73,669, Ki = 5 nM) have been postulated based on a computational model of the 1/HIV-PR complex. A novel macrocyclic inhibitor 8 (MDL 104,168) wherein the P1 and P3 side chains of the original acyclic inhibitor have been joined retains good biological activity (Ki = 20 nM). NMR analysis of the precursor alcohol (S)-7 shows the conformation of the cyclic region to be very similar to that observed in the enzyme-bound 8 as determined by the computational model. Consistency of the computational model with NMR data and in vacuo molecular dynamics simulations provide the basis for postulating further modifications of the cyclic inhibitor expected to optimize its interactions with HIV-PR.
Subject(s)
Dipeptides/chemistry , HIV Protease Inhibitors/chemistry , Peptides, Cyclic/chemistry , Amino Acid Sequence , Dipeptides/pharmacology , Drug Design , HIV Protease Inhibitors/pharmacology , Magnetic Resonance Spectroscopy , Models, Molecular , Molecular Sequence Data , Peptides, Cyclic/pharmacologySubject(s)
Acetophenones/pharmacology , Cholinesterase Inhibitors/pharmacology , Trimethylsilyl Compounds/pharmacology , Acetophenones/chemistry , Acetophenones/pharmacokinetics , Acetylcholinesterase/metabolism , Alzheimer Disease/drug therapy , Animals , Brain/drug effects , Brain/enzymology , Butyrylcholinesterase/metabolism , Cholinesterase Inhibitors/chemistry , Cholinesterase Inhibitors/pharmacokinetics , Dogs , Heart/drug effects , Humans , In Vitro Techniques , Kinetics , Male , Myocardium/enzymology , Rats , Rats, Sprague-Dawley , Trimethylsilyl Compounds/chemistry , Trimethylsilyl Compounds/pharmacokineticsSubject(s)
Methylamines/pharmacology , Monoamine Oxidase Inhibitors/pharmacology , Organosilicon Compounds/pharmacology , 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine/antagonists & inhibitors , Administration, Oral , Animals , Blood Pressure/drug effects , Brain/drug effects , Brain/enzymology , Heart Rate/drug effects , In Vitro Techniques , Kinetics , MPTP Poisoning , Male , Methylamines/administration & dosage , Methylamines/chemistry , Monoamine Oxidase/metabolism , Monoamine Oxidase Inhibitors/administration & dosage , Monoamine Oxidase Inhibitors/chemistry , Organosilicon Compounds/administration & dosage , Organosilicon Compounds/chemistry , Rats , Rats, Sprague-Dawley , Tyramine/toxicityABSTRACT
Comparison of MeO-Suc-Val-Pro-Phe-CO2Me (29) and MeO-Suc-Ala-Ala-Pro-Phe- CO2Me (25) with their corresponding trifluoromethyl ketones 9a and 9b, respectively, in rat and human neutrophil cathepsin G assays showed the alpha-keto esters to be more potent inhibitors. Likewise, Ac-Pro-Ala-Pro-Ala-CO2Me (21) was more potent than its corresponding trifluoromethyl ketone (9c) in both porcine pancreatic elastase and human neutrophil elastase assays. Within a set of Ala-Ala-Pro-Val-CF3 elastase inhibitors, the carbobenzyloxy (Cbz) N-protecting group conferred greater potency as a P5 site recognition unit for elastase than did dansyl, methoxysuccinyl, or tert-butyloxycarbonyl. Initial inhibition of elastase was greater when trifluoromethyl ketone 9f was added from a stock solution of dimethyl sulfoxide than when it had been buffer-equilibrated prior to assay, which suggests that the nonhydrated ketone is the more effective form of the inhibitor. The most potent elastase inhibitor we report is Na-(Ad-SO2)-N epsilon-(MeO-Suc)Lys-Pro-Val-CF3 (16) which has a Ki of 0.58 nM.
Subject(s)
Cathepsins/antagonists & inhibitors , Ketones/pharmacology , Neutrophils/enzymology , Oligopeptides/pharmacology , Pancreas/enzymology , Pancreatic Elastase/antagonists & inhibitors , Protease Inhibitors , Amino Acid Sequence , Animals , Cathepsin G , Chemical Phenomena , Chemistry , Humans , Ketones/chemical synthesis , Kinetics , Molecular Sequence Data , Molecular Structure , Oligopeptides/chemical synthesis , Rats , Serine Endopeptidases , Stereoisomerism , SwineABSTRACT
Renin inhibition has been evaluated for a new class of fluorinated ketones, true analogues of peptides that have been retroinverted at the C-terminal position. The readily formed hydrate of the ketone is proposed to mimic the tetrahedral intermediate that occurs during the enzyme-catalyzed hydrolysis of amide linkage. From this series of compounds it appears that the number of reverted amide bonds is crucial in terms of activity. Furthermore, a shortening of the C-terminal part of our peptide analogues and the replacement of the leucine residue in P1 by a cyclohexylalanine leads to the tripeptide analogue 12 a potent renin inhibitor (IC50 = 3.5 x 10(-9) M).
Subject(s)
Drug Design , Ketones , Oligopeptides , Renin/antagonists & inhibitors , Humans , Ketones/pharmacology , Molecular Structure , Oligopeptides/pharmacology , Renin/blood , Structure-Activity RelationshipABSTRACT
The alpha-silyl amines benzyl-dimethyl-silyl-methanamine and the p-fluoro and p-chloro derivatives are potent time-dependent inhibitors of rat brain MAO-B. The inhibition exhibits saturation kinetics, takes place in the enzyme active-site and is irreversible. The most potent inhibitor in the series is 4-fluorobenzyl-dimethyl-silyl-methanamine (KI = 11 microM, tau 1/2 = 2.3 min). Its selectivity for the B-form relative to the A-form of rat brain MAO is higher than 10(4). Benzyl-dimethyl-silyl-methanamines may represent a new family of anti-Parkinsonian agents.
Subject(s)
Methylamines/pharmacology , Monoamine Oxidase Inhibitors/pharmacology , Monoamine Oxidase/metabolism , Silicon/pharmacology , Animals , Benzylamines/pharmacology , Brain/drug effects , Brain/enzymology , Enzyme Activation/drug effects , Kinetics , Rats , Substrate SpecificityABSTRACT
The syntheses of alpha-mono- and alpha-difluoromethyl derivatives of tryptophan and 5-hydroxytryptophan are described. In an attempt to selectively regulate serotonin synthesis, alpha-(mono- and difluoromethyl)tryptophan were tested in vivo as precursors (or prodrugs) of their 5-hydroxy analogues. Although alpha-(mono- and difluoromethyl)-5-hydroxytryptophans are potent irreversible inhibitors of aromatic amino acid decarboxylase (equipotent to alpha-difluoromethyl-Dopa), only alpha-(monofluoromethyl)tryptophan affects the level of serotonin in vivo (small decrease), alpha-(difluoromethyl)tryptophan being a very poor substrate of the activating (or helper) enzyme, tryptophan hydroxylase.
Subject(s)
5-Hydroxytryptophan/analogs & derivatives , 5-Hydroxytryptophan/chemical synthesis , Brain/metabolism , Fluorides/pharmacology , Tryptophan/analogs & derivatives , Tryptophan/chemical synthesis , 5-Hydroxytryptophan/pharmacology , Amino Acids/metabolism , Animals , Brain/drug effects , Catecholamines/metabolism , Magnetic Resonance Spectroscopy , Male , Rats , Rats, Inbred Strains , Structure-Activity Relationship , Tryptophan/pharmacologyABSTRACT
beta-Difluoromethyl-beta-alanine (3-amino-4,4-difluorobutanoic acid) is a potent in vitro and in vivo inhibitor of GABA-T. The rate of inhibition of GABA-T is concentration- and time-dependent. The inactivation is active-site directed. No reactive species escapes from the active site before reacting with the enzyme. The inhibition is irreversible and stereospecific. The use of beta-2H-beta-difluoromethyl-beta-alanine results in a marked primary isotope effect in vitro and in vivo. The use of differently substituted dihalogeno derivatives of beta-alanine suggests that the rate of inhibition is dependent on the nature and position of the leaving group. The mechanism of inhibition is discussed on the basis of spectral changes.
Subject(s)
4-Aminobutyrate Transaminase/antagonists & inhibitors , Alanine/pharmacology , beta-Alanine/pharmacology , Animals , Brain/enzymology , Indicators and Reagents , Kinetics , Structure-Activity Relationship , Swine , beta-Alanine/analogs & derivatives , beta-Alanine/chemical synthesisABSTRACT
In vitro, 5-fluoropentane-1,4-diamine and 5,5-difluoropentane-1,4-diamine are potent enzyme-activated inhibitors of rat liver ornithine decarboxylase (EC 4.1.1.17). The two alpha-fluoromethyl derivatives of putrescine activate to different degrees S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50). The difluoromethyl derivative differs from the monofluoromethyl derivative in that it is not a substrate of diamine oxidase (EC 1.4.3.6), but is a better substrate of mitochondrial monoamine oxidase (EC 1.4.3.4) than the monofluoromethyl derivative. In vivo, a single i.p. injection of 200 mg/kg of 5-fluoropentane-1,4-diamine to rats causes a marked decrease of the ornithine decarboxylase activity in the ventral prostate and to a lesser extent in the thymus, whereas 5,5-difluoropentane-1,4-diamine causes only a slight decrease of this enzyme activity in the prostate and does not affect it in the thymus. Both compounds produce a decrease of 4-aminobutyrate: 2-oxoglutarate aminotransferase (EC 2.6.1.19) activity in the brain. The differences observed between the biochemical properties of the two alpha-fluoromethyl derivatives of putrescine are discussed in relation to the pKa value of the alpha-amino group which decreases from 7.75 for 5-fluoropentane-1,4-diamine to 6.4 for 5,5-difluoropentane-1,4-diamine.
Subject(s)
Carboxy-Lyases/antagonists & inhibitors , Ornithine Decarboxylase Inhibitors , Putrescine/analogs & derivatives , Animals , Chemical Phenomena , Chemistry , Kinetics , Liver/enzymology , Male , Prostate/enzymology , Putrescine/pharmacology , Rats , Rats, Inbred Strains , Testis/enzymology , Thymus Gland/enzymology , Time FactorsABSTRACT
omega-Monofluoromethyl and omega-difluoromethyl analogues of the known substrates of GABA-T, beta-alanine, gamma-aminobutyric acid, and 5-aminopentanoic acid, are time-dependent inhibitors of purified 4-aminobutyrate: 2-oxoglutarate aminotransferase (GABA-T). The inhibitory activity decreases with increasing chain length. In vitro, inhibitory activity decreases with increasing fluorine substitution of the methyl group. In vivo, beta-difluoromethyl-beta-alanine and 2,4-difluoro-3-aminobutyric acid are the most potent GABA-T inhibitors ever reported. Trifluoromethyl derivatives are devoid of GABA-T inhibitory activity in vitro or in vivo.
