Shotgun Kinetic Target-Guided Synthesis Approach Enables the Discovery of Small-Molecule Inhibitors against Pathogenic Free-Living Amoeba Glucokinases

Pathogenic free-living amoebae (pFLA) can cause life-threatening central nervous system (CNS) infections and warrant the investigation of new chemical agents to combat the rise of infection from these pathogens. Naegleria fowleri glucokinase (NfGlck), a key metabolic enzyme involved in generating glucose-6-phosphate, was previously identified as a potential target due to its limited sequence similarity with human Glck (HsGlck). Herein, we used our previously demonstrated multifragment kinetic target-guided synthesis (KTGS) screening strategy to identify inhibitors against pFLA glucokinases. Unlike the majority of previous KTGS reports, our current study implements a "shotgun" approach, where fragments were not biased by predetermined binding potentials. The study resulted in the identification of 12 inhibitors against 3 pFLA glucokinase enzymes─NfGlck, Balamuthia mandrillaris Glck (BmGlck), and Acanthamoeba castellanii Glck (AcGlck). This work demonstrates the utility of KTGS to identify small-molecule binders for biological targets where resolved X-ray crystal structures are not readily accessible.

caesius glucokinases in the sensitivity to carbon catabolite repression

Streptomyces peucetius var. caesius, the doxorubicin-producing strain, has two glucokinases (Glk) for glucose phosphorylation. One of them (ATP-Glk) uses adenosine triphosphate as its phosphate source, and the other one uses polyphosphate (PP). Glk regulates the carbon catabolite repression (CCR) process, as well as glucose utilization. However, in the streptomycetes, the specific role of each one of the Glks in these processes is unknown. With the use of PP- and ATP-Glk null mutants, we aimed to establish their respective role in glucose metabolism and their possible implication in the CCR. Our results supported that in S. peucetius var. caesius, both Glks allowed this strain to grow in different glucose concentrations. PP-Glk seems to be the main enzyme for glucose metabolism, and ATP-Glk is the only one involved in the CCR process affecting the levels of α-amylase and anthracycline production. Besides, analysis of Glk activities in the parental strain and the mutants revealed ATP-Glk as an enzyme negatively affected by high glucose concentrations. Although ATP-Glk utilizes only ATP as the substrate for glucose phosphorylation, probably PP-Glk can use either ATP or polyphosphate. Finally, a possible connection between both Glks may exist from the regulatory point of view.