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The Peculiar Case of the Hyper-thermostable Pyrimidine Nucleoside Phosphorylase from Thermus thermophilus*.

ABSTRACT: The poor solubility of many nucleosides and nucleobases in aqueous solution demands harsh reaction conditions (base, heat, cosolvent) in nucleoside phosphorylase-catalyzed processes to facilitate substrate loading beyond the low millimolar range. This, in turn, requires enzymes that can withstand these conditions. Herein, we report that the pyrimidine nucleoside phosphorylase from Thermus thermophilus is active over an exceptionally broad pH (4-10), temperature (up to 100 °C) and cosolvent space (up to 80 % (v/v) nonaqueous medium), and displays tremendous stability under harsh reaction conditions with predicted total turnover numbers of more than 10⁶ for various pyrimidine nucleosides. However, its use as a biocatalyst for preparative applications is critically limited due to its inhibition by nucleobases at low concentrations, which is unprecedented among nonspecific pyrimidine nucleoside phosphorylases.

SUBMITTER: Kaspar F

PROVIDER: S-EPMC8247850 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Thermal stable ?-glucosidases with transglycosylation activity could be applied to the industrial production of oligosaccharides as well as conjugation of sugars to biologically useful materials. Therefore, ?-glucosidases isolated from thermophiles have gained attention over the past decade. In this study, the characterization of a highly thermostable ?-glucosidase and its thermostability improved mutant from newly isolated strain Thermus thermophilus TC11 were investigated.The recombinant ?-glucosidase (TtAG) from Thermus thermophilus TC11 was expressed in Escherichia coli BL21 (DE3) and purified. The purified enzyme had a molecular mass of 184 kDa and consisted of 59-kDa subunits; it showed hydrolytic activity for pNP-?-D-glucopyranoside (pNPG), sucrose, trehalose, panose, and isomaltooligosaccharides and very low activity for maltose. The highest specific activity of 288.96 U/mg was observed for pNPG at 90 °C and pH 5.0; Pb(2+) provided a 20 % activity increase. TtAG was stable at 70 °C for more than 7 h and had a half-life of 195 min at 80 °C and 130 min at 90 °C. Transglycosylation activity was also observed with sucrose and trehalose as substrates. TtAG showed differences on substrate specificity, transglycosylation, multimerization, effects of metal ions and optimal pH from other reported Thermus ?-glucosidases. One single-substitution TtAG mutant Q10Y with improved thermostability was also obtained from random mutagenesis library. The site-saturation mutagenesis and structural modelling analysis indicated that Q10Y substitution stabilized TtAG structure via additional hydrogen bonding and hydrophobic interactions.Our findings indicate that TtAG is a highly thermostable and more acidic ?-glucosidase distinct from other reported Thermus ?-glucosidases. And this work also provides new insights into the catalytic and thermal tolerance mechanisms of ?-glucosidases, which may guide molecular engineering of ?-glucosidase and other thermostable enzymes for industrial application.

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The Peculiar Case of the Hyper-thermostable Pyrimidine Nucleoside Phosphorylase from Thermus thermophilus*.

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