Escherichia coli N-Acetylglucosamine-1-Phosphate-Uridyltransferase/Glucosamine-1-Phosphate-Acetyltransferase (GlmU) Inhibitory Activity of Terreic Acid Isolated from Aspergillus terreus

Abstract

Secondary metabolite of Aspergillus terreus, terreic acid, is a reported potent antibacterial that was identified more than 60 years ago, but its cellular target(s) are still unknown. Here we screen its activity against the acetyltransferase domain of a bifunctional enzyme, Escherichia coli N-acetylglucosamine-1-phosphate-uridyltransferase/glucosamine-1-phosphate-acetyltransferase (GlmU). An absorbance-based assay was used to screen terreic acid against the acetyltransferase activity of E. coli GlmU. Terreic acid was found to inhibit the acetyltransferase domain of E. coli GlmU with an IC 50 of 44.24 ± 1.85 µM. Mode of inhibition studies revealed that terreic acid was competitive with AcCoA and uncompetitive with GlcN-1-P. It also exhibited concentration-dependent killing of E. coli ATCC 25922 up to 4× minimum inhibitory concentration and inhibited the growth of biofilms generated by E. coli. Characterization of resistant mutants established mutation in the acetyltransferase domain of GlmU. Terreic acid was also found to be metabolically stable in the in vitro incubations with rat liver microsome in the presence of a NADPH regenerating system. The studies reported here suggest that terreic acid is a potent antimicrobial agent and support that E. coli GlmU acetyltransferase is a molecular target of terreic acid, resulting in its antibacterial activity.

Polyphasic taxonomy ofAspergillussectionCervini

“…Based on our results and other studies, several species in Aspergillus section Cervini produce terremutin, a precursor of the antibiotically active extrolite terreic acid (Guo et al., 2014, Sharma et al., 2016). Producers of terremutin include A. parvulus , A. nutans , A. cervinus , A. transcarpathicus , A. novoguineensis and A. christenseniae , and were formerly identified as the two first mentioned species (Elsohly et al., 1974, Phoebe et al., 1978).…”

Fungal Metabolites for the Control of Biofilm Infections

“…Apart from glucan-synthesis inhibition by antifungal compounds, a number of the metabolites reviewed here act through different mechanisms, some even combining more than one target. This is the case for terreic acid, which has been shown to inhibit two different bacterial biosynthetic enzymes [69,70]. The multi-target trait is a highly desired one when trying to avoid resistance development.…”

“…This is the case for terreic acid, which has been shown to inhibit two different bacterial biosynthetic enzymes [69,70]. The multi-target trait is a highly desired one when trying to avoid resistance development.…”

“…One of them, cytosporone E 27, could inhibit biofilm formation of methicillin-resistant S. aureus at 39 µM, about half of its MIC, and was also active against Plasmodium flaciparum [68]. Terreic acid 28, long known from Aspergillus terreus, has been demonstrated to suppress biofilm growth of E. coli by inhibiting the bifunctional GlmU uridyltransferase, which catalyzes the acetylation and uridylation of glucosamine-1-phosphate [69]. Natural products often have several rather than only one target in the cell, and terreic acid has also been shown to covalently inhibit the enzyme MurA, which catalyzes the reaction of this substrate with phosphoenolpyruvate [70].…”

Mutational analysis to identify the residues essential for the acetyltransferase activity of GlmU in Bacillus subtilis

“…28 The study of Ec-GlmU have conrmed that the N-terminal portion of the enzyme contains the uridylyltransferase domain and the C-terminus functions as an acetyltransferase. 29,30 The crystal structure of Ec-GlmU with multiple substrates revealed that the 2-amino group of GlcN-1-PO 4 is positioned in proximity to AcCoA to facilitate direct thioester attack by a ternary complex mechanism. 31,32 The cell wall structure of Gram-positive bacteria is quite different to that of Gram-negative bacteria.…”