Variability analyses of functional domains within glucosamine-6-phosphate synthase of mycosescausing fungi.

The immunosuppressive individuals are highly prone to get afflicted with invasive opportunistic fungal infections such as Candidiasis, Aspergillosis, Histoplasmosis, Coccidioidomycosis, Blastomycosis, Penicilliosis, Cryptococcosis and Zygomycosis which are becoming a cause of concern to the mankind due to their high morbidity and mortality rates. The existing antifungal agents are not completely effective due to their severe side-effects and recurrent drug resistance in fungi. Hence, there is an urgent need to develop newer and better antifungal drugs. The enzyme Glucosamine-6-phosphate (G-6-P) synthase catalyzes the ratelimiting step of the fungal cell-wall biosynthetic pathway and targeting it can inhibit the growth of the fungus. The present study attempts to investigate the inherent variations in functional domain viz. Glutaminase (GATase II) and Sugar Isomerising (SIS) of Glucosamine-6-phosphate (G-6-P) synthase enzyme of mycoses-causing fungi. These domains may be identified as probable active site(s). Multiple sequence alignment performed using ClustalX2 and construction of phylogenetic tree of individual domains by MEGA v5.0 helped in the analyses of several variable amino acid sites within the domains suggesting their vital role in the pathogenesis of the fungi. Further, the online server ConSurf implied that mostly, the highly conserved residues of the domains were functional and exposed on the surface of the active site, making it an easy target for the drugs. Consequently, variable analysis of functional domains of target implicated the importance of target specific drug discovery for the treatment of invasive fungal infections or mycoses.