Angiotensin converting enzyme from rabbit lung

Angiotensin converting enzyme from rabbit lung, hippuryl-L-histidyl-L-leucine, hippuric acid and HPLC grade acetonitrile, trifluoroacetic acid were purchased from Sigma Chemical Co. (St. Louis, Mo., U.S.A.). All the other reagents were analytical grade.

All chemical reagents and extraction solvents were of analytical grade and all analysis solvents were of HPLC grade. The angiotensin converting enzyme (from rabbit lung), histidine-l-hippuryl-l-leucine-chloride (HHL), Folin–Ciocalteu reagent, gallic acid and methanol were purchased from Sigma-Aldrich, Darmstadt, Germany. Borate saline buffer components (Boric acid, KCL and NaOH), dimethyl sulfoxide (DMSO), tris HCl and NaCl were purchased from Merck, Darmstadt, Germany.

Goat micellar casein (gMCC60) was provided by Ausnutria (Netherlands) and contained 63% protein and 22% lactose.
Trypsin (10–20% activity protein) was purchased from Novozymes (Bagsvaerd, Denmark). Pepsin (10000 NFU mg⁻¹) was purchased from China Pangbo Biological Engineering Co., Ltd. (Nanning, China). Angiotensin Converting Enzyme from rabbit lung, hippuryl-L-histidyl-L-leucine (HHL), and α-amylase (109.8 U mg⁻¹) were purchased from Sigma-Aldrich (USA). The Dulbecco's modified Eagle's medium (DMEM), phosphate-buffered saline (PBS), 0.25% Trypsin-EDTA, penicillin-streptomycin solution, and Fetal bovine serum (FBS) were purchased from Gibco Life Technologies (Grand Island, NY, USA). Angiotensin II (Ang II) and the Cell Counting Kit-8 were purchased from MedChemExpress (MEC, NJ, USA).

Water was purified using a Milli-Q Plus system from Millipore (Amsterdam, The Netherlands). Acetonitrile (ACN) (ULC/MS grade) and formic acid (FA) were obtained from Biosolve (Valkenswaard, The Netherlands). Tris, ZnCl₂, glycerol, hydrochloric acid, angiotensin-converting enzyme (ACE) from rabbit lung (≥2.0 units/mg protein), and captopril were obtained from Sigma-Aldrich (Zwijndrecht, The Netherlands). o-Aminobenzoylglycyl-p-nitro-l-phenylalanyl-l-proline (Abz-Gly-p-nitroPhe-Pro-OH; M1100) was obtained from Bachem (Bubendorf, Switzerland). DMSO was obtained from Riedel-de Haën (Zwijndrecht, The Netherlands). Most snake venoms were obtained commercially from Kentucky Reptile Zoo (USA), Ventoxin (USA), Biotoxin (USA), Venom Supplies (Tanunda, Australia), and African Reptiles & Venoms (Johannesburg, South Africa). The Boiga irregularis and Gloydius blomhoffii venoms were kind gifts from Prof. Steve Mackessy (University of Northern Colorado, USA) and Prof. Sadaaki Iwanaga (Kyushu University, Japan), respectively. Lyophilized venoms were kept at −20 °C. Prior to analysis, snake venoms were diluted in water to an end concentration of approximately 5.0 ± 0.1 mg/mL. After analysis, the samples were kept at −80 °C for later re-analysis.