coli DH5α containing only the pSUP202 vector check details (Figure 3B). Further, phospholipase A2 activity was examined in various subcellular fractions prepared from E. coli strain S299, including P505-15 manufacturer cytoplasm, cytoplasmic membrane, and outer membrane fractions. Most Plp activity was detected in Tween-20 soluble membrane fraction, indicating that Plp was
mainly localized in the cytoplasmic membrane of E. coli S299 (data not shown). No BODIPY-labeled free fatty acid (FFA) (at sn-1 position) was detected in the TLC analysis when an apolar solvent was used (data not shown), and BODIPY-labeled LPC was not further degraded by Plp in the reaction, indicating that Plp had no lysophospholipase or phospholipase B activity. Figure 3 Thin-layer chromatography (TLC) demonstrates
phospholipase A2 activity of Plp. BODIPY-labeled phosphatidylcholine (BPC) was incubated with various standard enzymes or sample preparations for 1 h at 37°C. Subsequently, the lipids were extracted GF120918 ic50 and separated by TLC. (A) The cleavage patterns of BPC by standard proteins PLA2, PLC, and PLD were able to distinguish the different phospholipase activities. (B) Cleavage patterns of BPC by supernatants (lanes 2 and 3) and cell lysates (lanes 4 and 5) from E. coli DH5α containing cloned plp (lanes 3 and 5) or just the cloning vector pSUP202 (lanes 2 and 4). Lane 1 contains only BPC incubated in the presence of PBS buffer. BLPC, BODIPY-labeled lysophosphatidylcholine; PA, phosphatic alcohol; PBt, phosphaticbutanol; DAG, di-acylglycerol. Enzymatic characteristics of rPlp protein To examine the enzymatic characteristics of Plp, the entire coding sequence of plp was cloned and inserted into the expression vector
pQE60, which adds a His6 (His-6×) tag to the carboxyl end of Plp. The over-expressed recombinant Plp (rPlp) formed inclusion bodies in E. coli. To recover many active rPlp, purification of the inclusion bodies followed by solubilization under mild conditions and re-folding was performed as described in the Methods. Purity of refolded rPlp protein was confirmed by SDS-PAGE and silver staining (data not shown). The final concentration of purified rPlp protein was 8 μg/ml with a recovery of <10%. Subsequently, the enzymatic characteristics of refolded rPlp were examined under various chemical and physical conditions. The enzymatic activity of rPlp positively correlated to its concentration from 1 μg/ml to 8 μg/ml (Figure 4A); therefore, 4 μg/ml rPlp protein was routinely used in other activity assays. The enzymatic activity unit of refolded rPlp (1 unit = amount of protein that cleaves 1 μmole of BODIPY-PC per minute) was about 2,500-fold higher than standard PLA2 enzyme extracted from porcine pancreas, which indicated that Plp had a high activity against the BPC phospholipid substrate. Plp enzyme activity exhibited a broad temperature optimum from 37°C to 64°C (Figure 4B) with 75% activity retained at 27°C and 50% activity at 20°C.