Isolation of cyclase, epimerase and a ring expansion enzyme for producing unnatural cephalosporins

摘要

The enzymes, cyclase, epimerase and a ring expansion enzyme, are isolated separately from a cell-free extract of a prokaryotic beta-lactam producing organism. The isolated enzymes are used to produce unnatural cephalosporins from polypeptide precursors. Isolation is carried out by adding ammonium sulfate to 40% saturation to the cell-free extract to precipitate contaminating proteins, adding ammonium sulfate to 70% saturation to the resultant supernatant to precipitate the enzymes, suspending the precipitated enzymes in a buffer, separating epimerase from the suspension by gel filtration, and separating cyclase and the ring expansion enzyme from each other by ion exchange chromatography.