Hydrolytic enzyme inhibitors

Gelman BB, Wolf DA, Rodriguez-Wolf M et al (1997) Mononuclear phagocyte hydrolytic enzyme activity associated with cerebral HIV-1 infection. Am J Pathol 151 1437-1446 Giraudon P, Buart S, Bernard A et al (1997) Cytokines secreted by gUal cells infected with HTLV-I modulate the expression of matrix metalloproteinases (MMPs) and their natural inhibitor (TIMPs) possible involvement in neurodegenerative processes. Mol Psychiatry 2(107-10) 84... 

Brief notes are added on phosphorofluoridates even though their destruction by microbial activity— though clearly possible—is limited by their toxicity to the requisite microorganisms. One of the motivations for their inclusion is the fact that the hydrolytic enzyme(s) responsible for defluorination—organophosphorus acid anhydrase (OPA)—is widespread, and is found in a number of bacteria (Landis and DeFrank 1990). The microbial hydrolysis of organophosphorus pesticides and cholinesterase inhibitors is accomplished by several distinct enzymes, which are collectively termed organophosphorus acid anhydrases (OPAs). These have been reviewed (DeFrank 1991), so that only a few additional comments are necessary. 

M.H. Gelb, J.P. Svaren, R.H. Abeles, Fluoro ketone inhibitors of hydrolytic enzymes, Biochemistry 24 (1985) 1813-1817. 

The presence of fluorine strongly destabihzes a carbocation centered on the jS carbon because only the inductive effect takes place. " The effect on solvolysis or protonation reaction of double bonds can be very important. The destabilization of carbenium and alkoxycarbenium ions plays an importantrole in the design of enzyme inhibitors (cf Chapter 7) and in the hydrolytic metabolism of active molecules (cf. Chapter 3). 

Trifluoromethyl /1-thioalkyls and /1-amino alcohols are often good reversible inhibitors of esterases and proteases, respectively. Depending on the enzymes (serine or aspartyl enzymes), fluorinated alcohols are often less efficient inhibitors than the corresponding ketones, which act as analogues of the transition state (vide infra). Nevertheless, fluoroalcohols inhibit hydrolytic enzymes with high inhibition constants (Figure 7.25)." ... 

Despite the numerous enzymology smdies with fluoroketones as inhibitors of hydrolytic enzymes, only a few of them have become drugs (cf. Chapter 7). Among them, we can cite a monofluoroketone (fluasterone. Figure 8.85), a difluoroketone... 

Birk, Y. (1987) Proteinase inhibitors. In Hydrolytic Enzymes (eds Neuberger, A. and Brocklehurst, K.). Elsevier (Biomedical Division), Amsterdam. 

In order to minimize waste as well as to direct selectivity, a number of approaches toward dissipation-control are being examined. For example, both volatilization and photodecomposition often can be regulated to a desired degree by incorporation of a non-volatile resin additive into the pesticide formulation (35). The technique appears promising for insecticides, and there is no reason to believe it should not work for herbicides also. Another approach is inhibition of microbial break-down for example, N-methylcarbamate inhibitors of hydrolytic enzymes, such as PCMC ( -chlorophenyl N-methylcarbamate), applied together with a herbicide such as chloropropham [isopropyl N-(3-chlorophenyl)carbamate] which is inactivated by soil microbes, more than doubled the effectiveness (36,37). 

Compounds effecting a stable intermediate in the course of enzymatic catalysis are a sort of mechanism-based inhibitor. However, in this case, the enzymatic activity lost by the formation of the intermediate can regenerate after a certain period. Compounds of this class are often observed for hydrolytic enzymes. The formation of an acyl enzyme intermediate (EA) is a characteristic feature of the reaction catalyzed by these enzymes, as shown in Eq. (6). Esters of p-guanidinobenzoate (9), which were discussed in Sect. 4.1, behave as transient inhibitors of trypsin due to the formation of a relatively stable acyl enzyme. A similar type of inhibition occurs in the temporary... 

Therefore, the main challenge in developing robust microbes is to ensure efficient fermentations of the heterogeneous substrates released from biomass materials in the presence of inhibitors and fermentation products and under restricted pH and temperature conditions to ensure maximum product production. For the SSF process, special considerations are needed in searching for new microbes to allow optimum activities of hydrolytic enzymes. For the CBP process, pathways for producing endogenous hydrolytic enzymes should be included in new microbes. 

Some other hydrolytic enzymes, in addition to proteases, that are important drug targets include protein phophatases, phosphodiesterases, nucleoside hydrolases, acetylhydolases, glycosylases, and phospholipases. Structure-based inhibitor design is currently being applied to a number of these enzymes. The last three mentioned have been successfully tar-... 

Diisopropylfluorophosphate, which irreversibly binds to active serine residues on some hydrolytic enzymes, is an example of this type of inhibitor, decreases because some enzyme is completely removed from the system. (Remember, = j>rE]i.) An irreversible inhibitor can be dis-... 

Tetrahedral transition state analogues of ester and amide substrates are known to function as efficient enzyme inhibitors of hydrolytic enzymes such as serine and aspartyl proteases as well as metalloproteinases (see Fig. 1.24) [141-144], Although ketals of alkyl or aryl ketones are usually not stable, those of difluroalkyl or trifluoromethyl ketones have considerable stability, as exemplified by their facile formations of the corresponding stable hydrates [145, 146]. Therefore, substrate analogues, containing difluoroalkyl or trifluoromethyl ketone moiety in appropriate positions, have been studied as effective transition state inhibitors of hydrolytic enzymes [141, 147-150],... 

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