Pepstatin

Pepstatin (see page 531) is an extremely potent inhibitor of the monomeric aspartic proteases, with A) valnes of less than 1 nM. 

Inhibitors which interact only with peptidases of one catalytic type include pepstatin (aspartic peptidases) E64 (cysteine peptidases from clan CA) diisopropyl fluorophosphates (DFP) and phenylmethane sulfonyl-fluoride (PMSF) (serine peptidases). Bestatin is a useful inhibitor of aminopeptidases. 

Poly(L-lysine) has also been suggested as a carrier for pepstatin, a specific inhibitor of the lysosomal proteinase cathepsin D, responsible for causing muscle-wasting diseases, such as muscular dystrophy [257],... 

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). 

K. Suguna, E. A. Padlan, R. Bott, J. Boger, K. D. Parris, and D. R. Davies, Structures of complexes of rhizopus pepsin with pepstatin and other statine-containing inhibitors, Proteins 13 195 (1992). 

H. Umezawa, T. Aoyagi, H. Morishima, M. Matsuzaki, and M. Hamada, Pepstatin, a new pepsin inhibitor produced by actinomycetes, J. Antibiot. (Tokyo) 23 259 (1970). 

D. H. Rich, and E. T. Sun, Mechanism of inhibition of pepsin by pepstatin. Effect of inhibitor structure on dissociation constant and time-dependent inhibition, Biochem. Pharmacol. 29 2205 (1980). 

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... 

Late infantile neuronal ceroid lipofuscinosis (CLN2) Autosomal recessive Pepstatin-insensitive lysosomal peptidase... 

The neuronal ceroid lipofuscinoses (CLN), also referred to as Batten s disease, are a group of disorders characterized by the accumulation of autofluorescent lipopigments. Clinical hallmarks include blindness, seizures, cognitive and motor decline and early death. Age of onset varies from infancy to adulthood. Eight genetic forms have been identified [4]. Two involve lysosomal acid hydrolases. CLN1 codes for palmitoyl protein thioesterase 1. Clinically it presents most often in infancy and leads to loss of active movement and visual contact by 3 years of age. It is most common in Finland, where its incidence is 1 20,000. CLN2 codes for a lysosomal pepstatin-insensitive acid protease. 

Wu et al. (1998) noted that doxombicin-induced apoptosis in lymphoid cells was blocked by pepstatin A, which is an inhibitor of cathepsin D. These investigators also observed that cathepsin D was induced through p53 DNA-binding sites at the cathepsin D promoter. Moreover, they have foimd that, compared to fibroblasts from wild-type mice, cathepsin D-/- fibroblasts from gene knock-out mice exhibited increased resistance to death caused by doxombicin. Also, in semm-deprived rat PC 12 cells undergoing apoptosis, the amoimt of cathepsin B has been observed to decline, while the level of cathepsin D increased (Shibata et al, 1998), and, in our laboratory (Kagedal et al, 2001), the same phenomenon was recently seen in human fibroblasts exposed to naphthazarin. 

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