Figure 4.

Recombinant B. subtilis and E. coli PxpABC proteins had 5-oxoprolinase activity. A, purified B. subtilis PxpA and PxpBC proteins containing an N- or C-terminal His tag were analyzed by SDS-PAGE and assayed for OPase activity. The positions of SDS-PAGE molecular weight markers (kDa) are indicated. Assays contained 10 μg of PxpBC (PxpB containing an N-terminal His tag), 4.4 μg of PxpA containing a C-terminal His-tag, and 5 mm ATP as indicated as in Fig. 3. B, OPase activity measured in lysates of E. coli cells harboring expression vector containing the E. coli pxpBCA genomic region. Data represent the mean ± S.E. of four purified protein preparations or three independent lysate preparations. †, not detectable (detection limit: 1.0 pmol min⁻¹ mg⁻¹ protein in purified protein assays; 0.3 pmol min⁻¹ mg⁻¹ protein in E. coli lysates).