Article

Identification of an Extremely Thermostable Enzyme with Dual Sugar-1-phosphate Nucleotidylyltransferase Activities from an Acidothermophilic Archaeon, Sulfolobus tokodaii strain 7

National Institute of Advanced Industrial Science and Technology, Higashi 1-1-1, Tsukuba, Ibaraki 305-8566, Japan.
Journal of Biological Chemistry (Impact Factor: 4.57). 04/2005; 280(10):9698-705. DOI: 10.1074/jbc.M411211200
Source: PubMed

ABSTRACT L-rhamnose is an essential component of the cell wall and plays roles in mediating virulence and adhesion to host tissues in many microorganisms. Glucose-1-phosphate thymidylyltransferase (RmlA, EC 2.7.7.24) catalyzes the first reaction of the four-step pathway of L-rhamnose biosynthesis, producing dTDP-D-glucose from dTTP and glucose-1-phosphate. Three RmlA homologues of varying size have been identified in the genome of a thermophilic archaeon, Sulfolobus tokodaii strain 7. In this study, we report the heterologous expression of the largest homologue (a 401 residue-long ST0452 protein) and characterization of its thermostable activity. RmlA enzymatic activity of this protein was detected from 65 to 100 degrees C, with a half-life of 60 min at 95 degrees C and 180 min at 80 degrees C. Analysis of a deletion mutant lacking the 170-residue C-terminal domain indicated that this region has an important role in the thermostability and activity of the protein. Analyses of substrate specificity indicated that the enzymatic activity of the full-length protein is capable of utilizing alpha-D-glucose-1-phosphate and N-acetyl-D-glucosamine-1-phosphate but not alpha-D-glucosamine-1-phosphate. However, the protein is capable of utilizing all four deoxyribonucleoside triphosphates and UTP. Thus, the ST0452 protein is an enzyme containing both glucose-1-phosphate thymidylyltransferase and N-acetyl-D-glucosamine-1-phosphate uridylyltransferase activities. This is the first report of a thermostable enzyme with dual sugar-1-phosphate nucleotidylyltransferase activities.

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    • "The predicted activity (Table 1) was assayed at 80°C with dTDP-D-glucose and UDP-D-glucose (Fig. 2). UDP-D-glucose was also used as a substrate candidate because UDP-D-glucose as well as dTDP-D-glucose can be produced by the product from the another rmlA homolog (Zhang et al., 2005). As shown in Fig. 2, dTDP-D-glucose was used as a substrate by RmlB, whereas UDP-D-glucose was not. "
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