Characterization of a novel metal-dependent D-psicose 3-epimerase from Clostridium scindens 35704.

ABSTRACT: The noncharacterized protein CLOSCI_02528 from Clostridium scindens ATCC 35704 was characterized as D-psicose 3-epimerase. The enzyme showed maximum activity at pH 7.5 and 60°C. The half-life of the enzyme at 50°C was 108 min, suggesting the enzyme was relatively thermostable. It was strictly metal-dependent and required Mn²? as optimum cofactor for activity. In addition, Mn²? improved the structural stability during both heat- and urea-induced unfolding. Using circular dichroism measurements, the apparent melting temperature (T m) and the urea midtransition concentration (C m) of metal-free enzyme were 64.4°C and 2.68 M. By comparison, the Mn²?-bound enzyme showed higher T m and C m with 67.3°C and 5.09 M. The Michaelis-Menten constant (K m), turnover number (k cat), and catalytic efficiency (k cat/K m) values for substrate D-psicose were estimated to be 28.3 mM, 1826.8 s?¹, and 64.5 mM?¹ s?¹, respectively. The enzyme could effectively produce D-psicose from D-fructose with the turnover ratio of 28%.

SUBMITTER: Zhang W 

PROVIDER: S-EPMC3639893 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature