Abstract Description

Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species (ESKAPE) pathogens are the leading cause of nosocomial infections, and their multidrug resistance profile poses a major threat to global public health. The inadequate availability of effective antimicrobial therapies coupled with the rapid increase in resistance necessitates the discovery of new drug templates. A well-established and successful strategy in antimicrobial drug discovery is the identification of inhibitors that target essential microbial enzymes, those critical for pathogen survival. The establishment of reliable enzyme assay platforms has become a critical step in evaluating the bioactivity of natural products and advancing them toward further investigation. Notable targets that have been established for our drug discovery enzyme platform include S. aureus pyruvate kinases - a key glycolytic enzyme involved in energy metabolism, 7,8-Dihydro-6-hydroxymethylpterin-pyrophosphokinase (HPPK) - a crucial enzyme in folate biosynthesis, and -deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) – an enzyme involved in the Gram-negative MEP isoprenoid biosynthetic pathway. A diverse library of marine natural products (MNPs) and microbial extracts was screened, revealing several promising candidates with selective inhibitory activity against these specific enzymes. Topsentin compounds isolated from the Topsentia sponge species inhibited the S. aureus pyruvate kinase enzyme. Marine sponge extracts from Ascidians, Psammocinia species and Tsitsikamma species demonstrate inhibitory effects on the S. enterica and A. baumannii DXR enzyme. Chalinidae and Thorectidae species have shown the potential to inhibit the E. coli, A. baumannii and S. aureus HPPK enzyme. Additionally, Streptomyces globisporus, an actinobacterial strain, has shown potential inhibitory activity against the E. coli and A. baumannii HPPK enzyme. The results of the screening pipeline support the potential of HPPK/DXR/PK enzymes as targets for natural product-based inhibitors. The identification of several active natural product extracts, particularly those with selectivity against Gram-negative bacteria, provides a solid foundation for further investigation.