The Saccharomyces cerevisiae gene, YFL017C, for a putative acetyltransferase was characterized. Disruption of YFL017C was lethal, leading to a morphology similar to those caused by the depletion of AGM1 or UAP1, the genes encoding phospho-N-acetylglucosamine mutase and UDP-N-acetylglucosamine pyrophosphorylase, respectively. This implies the involvement of YFL017C in UDP-N-acetylglucosamine synthesis. The recombinant protein for YFL017C displayed phosphoglucosamine acetyltransferase activities

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... n vitro and utilized glucosamine 6-phosphate as the substrate. When incubated with Agm1p and Uap1p, the Yfl017c protein produced UDP-N-acetylglucosamine from glucosamine 6-phosphate. These results indicate that YFL017C specifies glucosamine-6-phosphate acetyltransferase; therefore, the gene was designated GNA1 (glucosamine-6phosphate acetyltransferase). In addition, whereas bacterial phosphoglucosamine acetyltransferase and UDP-N-acetylglucosamine pyrophosphorylase activities are intrinsic in a single polypeptide, they are encoded by distinct essential genes in yeast. When the sequence of ScGna1p was compared with those of other acetyltransferases, Ile 97 , Glu 98 , Val 102 , Gly 112 , Leu 115 , Ile 116 , Phe 142 , Tyr 143 , and Gly 147 were found to be highly conserved. When alanine was substituted for these amino acids, the enzyme activity for the substituted Phe 142 or Tyr 143 enzymes was severely diminished. Although the activity of Y143A was too low to perform kinetics, F142A displayed a significantly increased K m value for acetyl-CoA, suggesting that the Phe 142 and Tyr 143 residues are essential for the catalysis. Acetyltransferases catalyze the acetylation of their specific substrates using the cofactor acetyl-CoA (Ac-CoA). These enzymes play important roles in a wide variety of biological processes, including metabolism, chromatin structure, gene expression, and cell cycle (1-3). At least one acetyltransferase is necessary for the biosynthesis of UDP-N-acetylglucosamine (UDP-GlcNAc), which is an essential metabolite both in pro-1 The abbreviations used are: ORF, open reading frame; GST, glutathione S-transferase.