Identification of novel acetyltransferase activity on the thermostable protein ST0452 from Sulfolobus tokodaii strain 7.

A 401-residue-long protein, ST0452, has been identified from a thermophilic archaeon, Sulfolobus tokodaii strain 7, as a glucose-1-phosphate thymidylyltransferase (Glc-1-P TTase) homolog with a 170-residue-long extra C-terminus portion. Functional analyses of the ST0452 protein have confirmed that the protein possessed dual sugar-1-phosphate nucleotidylyltransferase (sugar-1-P NTase) activities. The 24 repeats of a signature motif sequence which has been found in bacterial acetyltransferases, (L/I/V)-(G/A/E/D)-XX-(S/T/A/V)-X, were detected at the C terminus of the ST0452 protein. This observation prompted our group to investigate the acetyltransferase activity of the ST0452 protein. Detection of the release of coenzyme A (CoA) from acetyl-CoA and the production of UDP-N-acetyl-d-glucosamine (UDP-GlcNAc) from glucosamine-1-phosphate (GlcN-1-P) and UTP in the presence of the ST0452 protein revealed that this protein possesses the GlcN-1-P-specific acetyltransferase activity. In addition, analyses of substrate specificity showed that acetyltransferase activity of the ST0452 protein is capable of catalyzing the change of galactosamine-1-phosphate (GalN-1-P) to N-acetyl-d-galactosamine-1-phosphate (GalNAc-1-P) as well as GlcN-1-P and that its sugar-1-P NTase activity is capable of producing UDP-GalNAc from GalNAc-1-P and UTP. This is the first report of a thermostable bifunctional enzyme with GalN-1-P acetyltransferase and GalNAc-1-P uridyltransferase activities. The observation reveals that the bacteria-type UDP-GlcNAc biosynthetic pathway from fructose-6-phospate is utilized in this archaeon and represents a novel biosynthetic pathway for producing UDP-GalNAc from GalN-1-P in this microorganism.