Identification and characterization of the genes for N-acetylglucosaminekinase and N-acetylglucosamine-phosphate deacetylase in the pathogenic fungusCandida albicans

Like bacteria and many fungi, the pathogenic fungus Candida albicans can ut ilize GlcNAc as a carbon source for growth. A cluster of six genes was iden tified in the C. albicans genome. One of the genes in the cluster was CaNAG 1, which is responsible for GlcN6P deaminase and is therefore essential for GlcNAc-dependent growth. The other five genes were designated CaNAG2, CaNA G3, CaNAG4, CaNAG5 and CaNAG6. The mRNA levels of CaNAG1, CaNAG2 and CaNAG5 were significantly induced by GlcNAc, whereas those of CaNAG3, CaNAG4 and CaNAG6 were not. Neither CaNAG2 nor CaNAG5 was essential for growth, but di sruption of CaNAG2 or CaNAG5 greatly retarded the growth of cells using Glc NAc as the sole carbon source. Although no homolog of CaNAG2 or CaNAG5 was found in the Saccharomyces cerevisiae genome, CaNag2p displayed sequence si milarities to Escherichia coli nagA, and CaNag5p is homologous to a wide va riety of hexose kinases. When expressed as a fusion protein with glutathion e S-transferase (GST), CaNag5p produced GlcNAc-P from GlcNAc in the presenc e of ATP, whereas GST alone did not. Furthermore, the recombinant GST-CaNag 2p fusion protein converted GlcNAcP, which was produced by aNag5p, into Glc NP. These results clearly demonstrate that CaNAG2 and CaNAG5 encode GlcNAcP deacetylase and GlcNAc kinase, respectively. CaNag5p recognized glucose an d mannose as substrates, whereas the recently identified human GlcNAc kinas e was specific to GlcNAc. Deletion of CaNAG2 or CaNAG5 markedly, and that o f CaNAG1 moderately, attenuated the virulence of C. albicans in a mouse sys temic infection model. Thus, it appears that GlcNAc metabolism of C. albica ns is closely associated with its virulence.