TABLE 1.

Total yield and kinetic parameters of purified TrxR induced at different expression levels in LB medium with the pBAD expression system

Arabinose (%)pSUABCRecovereda (mg/liter)Recovereda (mg/liter/OD600)kcat (min−1)Km (mM)kcat/Km (min−1 mM−1)U/mgbRecovered selenoproteinc (mg/liter/OD600)
0.00025.83.8250.151670.20.02
+9.35.71590.131,2231.40.23
0.00513.49.51230.186831.10.30
+29.218.23150.132,4232.71.40
0.213.69.8810.126750.70.20
+24.215.26460.173,8005.62.43
  • a Total recombinant TrxR (mixture of truncated and full-length forms) recovered in purification, given as yield per liter of original medium or per liter and OD600 unit.

  • b One unit is defined as the reduction of 1 μmol of DTNB per min in the standard DTNB assay (2). The specific activity of native mammalian TrxR is approximately 35 U/mg (2).

  • c Selenoprotein (full-length TrxR) recovered in the purification, given as yield per original culture volume and OD600 unit, as calculated from units per milligram and total recovered yield, assuming 35 U/mg for the full- length selenoprotein (2).