Uridine diphosphate N-acetylglucosamine homeostasis via CgNgk1 kinase modulates chitin levels and cell-wall integrity in Candida glabrata.

Candida glabrata is a clinically significant cause of candidemia, yet how it supplies uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc) for cell-wall chitin synthesis remains unclear. Here, we identify an N-acetylglucosamine (GlcNAc) kinase encoded by CAGL0M00682g and designated CgNgk1. In vitro, purified CgNgk1 preferentially phosphorylated GlcNAc with markedly higher catalytic efficiency than other sugars and accepted multiple nucleoside triphosphates, including ATP, as phosphoryl donors. Site-directed mutagenesis indicated that Asp197 and Lys155 are required for catalysis and ATP binding, respectively. In vivo, CgNgk1 overexpression in C. glabrata increased intracellular UDP-GlcNAc in a GlcNAc dose-dependent manner, whereas the kinase-dead D197N variant had no effect. CgNgk1-mediated GlcNAc phosphorylation elevated cell-wall chitin and heightened sensitivity to sodium dodecyl sulfate, heat, and low pH, but did not affect β-1,3-glucan-related phenotypes such as zymolyase or caspofungin sensitivity. Under GlcNAc supplementation, CgNgk1-overexpression specifically decreased cellular susceptibility to flucytosine, while responses to voriconazole and amphotericin B were unchanged. Overexpression of the putative hexosamine-pathway regulator CgIsr1 lowered intracellular UDP-GlcNAc, consistent with an intact endogenous pathway. These findings demonstrate that imported GlcNAc is routed via CgNgk1 to UDP-GlcNAc to promote chitin biosynthesis, and that quantitative control of this route shapes cell-wall integrity and modulates responses to host-relevant stresses and antifungal agents.