Abstract

Rapid resistance development of HIV-1 and Plasmodium falciparum parasite requires discovery of more potent new drugs. Aspartic protease enzymes expressed by HIV-1 and P. falciparum could be used as important drug targets. The catalytic site is located at the bottom of a cleft in the enzyme surface and consists of triad Asp25, Thr26, Gly27. Important aspartic acids are Asp32 and Asp215. Aspartic proteases are inhibited by pepstatin-A, a naturally occurring peptide containing two statins, which replace the amino acids. The hydroxyl group of the statin binds tightly to the catalytically-active aspartic acid residues in the active site of protease, thereby mimicking the transition state of the peptide cleavage. Previous study proved that ganoderiol-F, a triterpenoid isolated from the stem of Ganoderma sinense showed higher affinity towards HIV-1 protease (binding energy= -11.40 kcal/mol and K_i= 4.68 nM) than to plasmepsin I (binding energy= -9.96 kcal/mol and K_i= 50.94 nM). In this paper, computational studies of G. lucidum triterpenoids with aspartic protease enzymes of HIV-1 and plasmepsin I, were performed using AutoDock 4.2. Nelfinavir and KNI-10006 were used as the standards for HIV-1 protease and plasmepsin I, respectively. The four triterpenoids are able to interact with both enzymes. Ganoderat acid-B showed the best affinity to HIV-1 protease (binding energy= -7.49 kcal/mol and Ki= 0.001 mM) which is better than nelfinavir. Furthermore, the best affinity to Plasmepsin I is showed by ganodermanondiol (binding energy= -7.14 kcal/mol and Ki= 0.005 mM which is better than KNI-10006. According to the values of binding energy and inhibition constant, triterpenoids of G. lucidum could be developed further as both anti-HIV and anti-malaria.

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