Dithiothreitol (DTT), kanamycin monosulfate, lysozyme, and ampicillin (AMP) were purchased from GoldBio. Protease-inhibitors aprotinin, pepstatin A, and leupeptin were purchased from Sigma-Aldrich. HisPur™ Ni-NTA Resin was purchased from Thermo Fisher. All other buffers and reagents were purchased from Sigma-Aldrich or Thermo Fisher. The substrate pnitrophenyl phosphate (pNPP) was synthesized using a published method.