Of pepstatin

The change in the free energy with the mutation of the proton position is about 7.0 kcal/mol, in the presence of an ammonium ion, suggesting that the initial state is stable compared to the final state. In the presence of pepstatin the results suggest a barrier of about 1.0 kcal/mol for the transfer of proton from one site to the other site. This low energy barrier should allow the proton to shuttle between the two sites. The same barrier of about 1.0... 

The free energy perturbation calculations on mutation of the central statine residue of pepstatin to its dehydroxy and other derivatives were carried out using the window method. The crystal structure reported by Suguna et al.l4 l5was used for these calculations. In most simulations, the mutations were achieved either in 101 or 51 windows with 0.4 ps of equilibration and 0.4 ps of data collection at each window. The calculation for each mutation was repeated in water to determine the difference in the free energies of solvation and to complete the thermodynamic cycle. 

The mutation of the hydroxyl group positioned in R-configuration at the C(3) atom of the central statine (rSta) residue of the inhibitor gives rise to AAGbind of -0.51 kcal/mol, which is very close to the experimental value of -0.8 kcal/mol. It may be noted here that the starting configuration of the inhibitor in the enzyme-inhibitor complex is the same as that of pepstatin. The crystal structure of rhizopus pepsin or any other aspartic proteinase... 

B. G. Rao, and U. C. Singh, Studies on the binding of pepstatin and its derivatives to Rhizopus pepsin by quantum methanics, molecular mechanics, and free energy perturbation methods, J. Am. Chem. Soc. 113 6735 (1991). 

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... 

Figure 2. Stereo view of pepstatin bound in the R. chinensis pepsin active site. C-3 of statine carrying an OH group is indicated by the . Availability for hydrogen bonding is indicated by closeness of carboxyl groups of Asp-220 and Asp-32 to the statine hydroxyl and to each other.

We have approached this problem by studying the interactions between pepsin and ketones with structures based on that of pepstatin. Our strategy was to design ketones which would serve as pseudosubstrates, that is, be subject to the catalytic action of the enzyme, but only to the point of formation of a tetrahedral intermediate which, because of the increased stability of a C-C vs a C-N bond, would not break down to products. Such a stable tetrahedral intermediate would then, in principle, be amenable to study by the appropriate physical methods. appeared to be an ideal method since changes... 

Nisato, D., Wagnon, J., Callet, G., et al. (1987) Renin inhibitors. Free-Wilson and correlation analysis of the inhibitory potency of a series of pepstatin analogs on plasma renin. J Med Chem 30(12), 2287-2291. 

Reddy, D., Payens, T. A. and Brown, R. J. 1986. Effect of pepstatin on the chymosin-triggered coagulation of casein micelles. J. Dairy Sci. 69 (Suppl. 1), 72. 

Oyama, H., Abe, S., Ushiyama, S., Takahashi, S., and Oda, K. (1999). Identification of catalytic residues of pepstatin-insensitive carboxyl proteinases from prokaryotes by site-directed mutagenesis. J. Biol. Chem., 274, 27815-27822. 

Nonapeptide hnear amides are also often synthesized using the carbodiimide method. Examples include the synthesis of norcardicine A and the synthesis of renin inhibitors. The total synthesis of a trifluoromethyl (Tfm) analogue of pepstatin uses EDCCl/HOBt in the condensation steps. ... 

The reductive defluorination-alkylation method shown in Scheme 10.12 was successfully applied to the synthesis of A -Boc-Sta-xF[CF=CH]-Ala ethyl ester 51, which mimics the central Sta-Ala unit of pepstatin, a naturally occurring inhibitor of aspartyl proteases including renin, pepsin, HIV-1 and HIV-2 proteases (see Figure 10.3) [27]. 

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