Glutamine analogues containing a keto function – novel inhibitors of fungal glucosamine-6-phosphate synthase

Inhibitors of glucosamine-6-phosphate synthase as potential antimicrobials or antidiabetics - synthesis and properties

Glucosamine-6-phosphate synthase (GlcN-6-P synthase) is known as a promising target for antimicrobial agents and antidiabetics. Several compounds of natural or synthetic origin have been identified as inhibitors of this enzyme. This set comprises highly selective l-glutamine, amino sugar phosphate or transition state intermediate cis-enolamine analogues. Relatively low antimicrobial activity of these inhibitors, poorly penetrating microbial cell membranes, has been improved using the pro-drug approach. On the other hand, a number of heterocyclic and polycyclic compounds demonstrating antimicrobial activity have been presented as putative inhibitors of the enzyme, based on the results of molecular docking to GlcN-6-P synthase matrix. The most active compounds of this group could be considered promising leads for development of novel antimicrobial drugs or antidiabetics, provided their selective toxicity is confirmed.

Recent Progress in the Discovery of Antifungal Agents Targeting the Cell Wall

Due to the limit of available treatments and the emergence of drug resistance in the clinic, invasive fungal infections are an intractable problem with high morbidity and mortality. The cell wall, as a fungi-specific structure, is an appealing target for the discovery and development of novel and low-toxic antifungal agents. In an attempt to accelerate the discovery of novel cell wall targeted drugs, this Perspective will provide a comprehensive review of the progress made to date on the development of fungal cell wall inhibitors. Specifically, this review will focus on the targets, discovery process, chemical structures, antifungal activities, and structure-activity relationships. Although two types of cell wall antifungal agents are clinically available or in clinical trials, it is still a long way for the other cell wall targeted inhibitors to be translated into clinical applications. Future efforts should be focused on the identification of inhibitors against novel conserved cell wall targets.

Emerging Anticancer Activity of Candidal Glucoseamine-6-Phosphate Synthase Inhibitors upon Nanoparticle-Mediated Delivery

Numerous glutamine analogues have been reported as irreversible inhibitors of the glucosamine-6-phosphate (GlcN-6-P) synthase in pathogenic Candida albicans in the last 3.5 decades. Among the reported inhibitors, the most effective N³-(4-methoxyfumaroyl)-l-2,3-diaminopropanoic acid (FMDP) has been extensively studied in order to develop its more active analogues. Several peptide-FMDP conjugates were tested to deliver FMDP to its subcellularly located GlcN-6-P synthase target. However, the rapid development of fungal resistance to FMDP-peptides required development of different therapeutic approaches to tackle antifungal resistance. In the current state of the global antifungal resistance, subcellular delivery of FMDP via free diffusion or endocytosis has become crucial. In this study, we report on in vitro nanomedical applications of FMDP and one of its ketoacid analogues, N³- trans-4-oxo-4-phenyl-2-butenoyl-l-2,3-diaminopropanoic acid (BADP). FMDP and BADP covalently attached to polyethylene glycol-coated iron oxide/silica core-shell nanoparticles are tested against intrinsically multidrug-resistant C. albicans. Three different human cancer cell lines potentially overexpressing the GlcN-6-P synthase enzyme are tested to demonstrate the immediate inhibitory effects of nanoparticle conjugates against mammalian cells. It is shown that nanoparticle-mediated delivery transforms FMDP and BADP into strong anticancer agents by inhibiting the growth of the tested cancer cells, whereas their anti-Candidal activity is decreased. This study discusses the emerging inhibitory effect of the FMDP/BADP-nanoparticle conjugates based on their cellular internalization efficiency and biocompatibility.