Protease enzyme inhibition

Many of the early examples of maerocyeles in drug discovery relied on these classical reaction types for the formation of the ring and they remain in regular use. This was due, in part, to the peptidomimetic nature of many of these structures, which often were targeted at protease enzyme inhibition, and thus lent themselves readily to macrolactamization for amide bond formation or macrolactonization for cyclic depsipeptide-like compounds. Representative examples of these two general transformations are shown in Scheme 11.1 (BOP (benzotriazol-l-ylo5ytris(dimethylamino)-phosphonium hexafluorophosphate, Castro s reagent), EDC (l-ethyl-3-(3-dimethylamino-propyl)-carbodiimide), DMAP (4-dimethylamino-pyridine)) for the matrix metalloproteinase (MMP) inhibitor template 2 and the renin inhibitor scaffold 4. °... 

Biocatalysis has emerged as an important tool for the enantioselective synthesis of chiral pharmaceutical intermediates and several review articles have been published in recent years [133-137]. For example, quinuclidinol is a common pharmacophore of neuromodulators acting on muscarinic receptors (Figure 6.50). (JJ)-Quinudidin-3-ol was prepared via Aspergillus melleus protease-mediated enantioselective hydrolysis of the racemic butyrate [54,138]. Calcium hydroxide served as a scavenger of butyric acid to prevent enzyme inhibition and the unwanted (R) enantiomer was racemized over Raney Co under hydrogen for recycling. 

Protease inhibitor A drug that acts by inhibiting the viral protease enzyme, which prevents long strands of protein from being cleaved into the smaller proteins the virus requires for assembly. 

D. H. Rich, M. S. Bematowicz, N. S. Agarwal, M. Kawai, F. G. Salituro, and P. G. Schmidt, Inhibition of aspartic proteases by pepstatin and 3-methylstatine derivatives of pepstatin. Evidence for collected-substrate enzyme inhibition, Biochemistry 24 3165... 

The protective antiprotease -antitrypsin (AAT) inhibits several protease enzymes, including neutrophil elastase. In the presence of unopposed AAT activity, elastase attacks elastin, which is a major component of alveolar walls. A hereditary deficiency of AAT results in an increased risk for premature development of emphysema. In the inherited disease, there is an absolute deficiency of AAT. In emphysema resulting from cigarettesmoking, the imbalance is associated with increased protease activity or reduced activity of antiproteases. Activated inflammatory cells release several other proteases, including cathepsins and metalloproteinases. In addition, oxidative stress reduces antiprotease (or protective) activity. 

C5a is inactivated by the myeloperoxidase-H202 system, which oxidises a methionine residue (Met 70) on the molecule group A streptococcal endo-proteinases also abolish chemotactic activity of C5a and related compounds. Neutrophil lysosomal enzymes (e.g. elastase and cathepsin G) also destroy C5a chemotactic activity, but as these proteases are inhibited by the serum antiproteinases, a -antiproteinase and a2-macroglobulin, the physiological role of neutrophilic proteases in the inactivation of C5a is questionable. Two chemotactic factor inactivators have been found in human serum an a-globulin that specifically and irreversibly inactivates C5-derived chemotactic factors, and a / -globulin that inactivates bacterial chemotactic factors. These activities are heat labile (destroyed by treatment at 56 °C for 30 min) and are distinct from those attributable to anaphylatoxin inactivator. An apparently specific inhibitor of C5-derived chemotactic activity has also been described in human synovial fluid and peritoneal fluid. This factor (molecular mass of 40 kDa) is heat stable and acts directly on C5a. 

The hormone-hke peptide incretin stimulates the release of insuhn by a feedback process that involves cleaving the molecule to an inactive form. The protease enzyme dipeptidal peptidase (DPP) in turn cleaves incretin, in effect inactivating this enzyme. Inhibition of DPP consequently extends the action of incretin. This inhibition thus prevents the increased levels of blood glucose that mark diabetes. The protease inhibitor vidagliptin, which is modeled in part on the terminal sequence in DPP, has been found to sustain levels of insulin in Type II diabetics. The inhibition is apparently reversible in spite of the presence in the structure of the relatively reactive a-aminonitrile function. Construction of one intermediate in the convergent synthesis comprises the reaction of amino adamantamine (21-1) with a mixture of nitric and... 

The formation of the oxyanion intermediate during serine protease action is also supported by the existence of tetrahedral forms of enzymes inhibited by substratelike aldehydes. The -OH group of Ser 195 can add to the carbonyl group to form hemiacetals. For example, a 13C-enriched aldehyde whose carbonyl carbon had a chemical shift of 204 ppm gave a 94 ppm resonance as it formed the tetrahedral hemiacetal with one of the inhibitory aldehydes, N-ace tyl-i -Len-i-Leu-L-arginal... 

A straightforward approach is to hunt for short polypeptides that meet the specificity requirement of an enzyme but which, because of peculiarities of the sequence, are acted upon very slowly. Such a peptide may contain unusual or chemically modified amino acids. For example, the peptide Thr-Pro-nVal-NMeLeu-Tyr-Thr (nVal=norvaline NMeLeu = N-methylleucine) is a very slow elastase substrate whose binding can be studied by X-ray diffraction and NMR spectroscopy.6 Thiol proteases are inhibited by succinyl-Gln-Val-Val-Ala-Ala-p-nitroanilide, which includes a sequence common to a number of naturally occurring peptide inhibitors called cystatins.f They are found in various animal tissues where they inhibit cysteine proteases. 

In the life cycle of HIV, its RNA is translated into a polypeptide chain that is composed of several individual proteins including protease, integrase and reverse transcriptase, but in this form these enzymes are not functional. They must be cleaved by viral proteases from the assembled sequence in order for them to become functional. These posttranslational modifications allow the enzymes to facilitate the production of new viruses. The protease itself is made up of two 99-amino-acid monomers, and an aspartic acid residue in the monomer is required for the cleavage. The protease inhibitors inhibit the enzyme protease and consequently interfere with viral replication and maturation by preventing proteases from cleaving proteins into peptides. In humans, these drugs inhibit cleavage of HIV gag and pol polyproteins, which are part of the essential viral structural components, P7, P9, P17 and P24, and... 

Pis inhibit the digestive protease enzyme of HIV, which it uses to break the proteins of healthy cells into smaller pieces. These infected smaller pieces of protein then carry on infecting new host cells. Pis therefore slow down HIV proteases and subsequently inhibit the infection of new cells [94]. 

Ghorobekova (1987) showed the inhibitory effect of humic matter on protease activity. Inhibition kinetics are of mixed order, and humic acids can be used as a regulator of activity and biosynthesis of proteolytic enzymes. 

The original DEBS 1-TE cell-free system allowed several other features of polyketide chain extension to be examined by using well-known inhibitors of specific enzyme activities. Incubation of DEBS 1 -TE with the serine protease inhibitor phenylmethylsulfonyl fluoride (PMSF) resulted in a significant decrease in biosynthetic activity. This result emphasized the mechanistic similarity between the targeted TE domain and the serine protease enzymes. Addition of the fatty acid inhibitor cerulenin [38] also reduced production of the lactone, consistent with the evolutionary kinship between these two classes of enzymes. Inhibition of DEBS 1+TE by cerulenin was also reported [33],... 

Sortino et al. reported the use of light irradiation on SAMs supporting the anticancer drug flutamide to study its photoreactivity and product release of nitric oxide. The authors were able to conduct studies in the absence of noxious side effects such as singlet-oxygen photosensitization and observed that nitric oxide production halted when the light was turned off [103], Another photoactive molecule, azobenzene, has recently been exploited in the SAM community to aid in studies on cell adhesion and enzyme inhibition [104], Pearson and coworkers described the use of photoisomerizable SAMs of azobenzene to conduct a series of serine and cysteine protease inhibition experiments. When light of 340-380 nm is used, the... 

Human neutrophil elastase (HNE) is a serine containing enzyme which is one of the most destructive of proteolytic enzymes, being able to catalyze the hydrolysis of the components of connective tissue. It has been implicated in the development of diseases such as emphysema, cystic fibrosis, and rheumatoid arthrisis. /3-Sultams are excellent candidates for exploring the mechanism of sulfonation and possible inhibition of serine protease enzymes. A-Benzoyl... 

---