Angiotensin 1 converting enzyme

Soy protein powder was purchased from Harbin Gaoke Group Co., Ltd. Enzymes including alkaline proteinase (200 U/mg), papain (800 U/mg), trypsin from porcine pancreas (250 U/mg), pepsin from porcine gastric mucosa (500 U/mg), and pancreatin from porcine pancreas were purchased from the Summus Chemical Company; 4‐nitrophenyl‐α‐D‐glucopyranoside (PNPG), α‐glucosidase from Saccharomyces cerevisiae, acarbose hydrate; dipeptidyl peptidase IV (DPP‐IV) from human; gly‐pro‐p‐nitroanilide, hippuryl‐l‐histidyl‐l‐leucine (HHL), angiotensin I‐converting enzyme (ACE) from rabbit lung (2.0 U/mg); and hippuric acid (HA), DEAE‐52, and gel Sephadex G‐15 were obtained from Sigma‐Aldrich. All other chemicals and reagents were of analytical grade and commercially available.

The enzymes used for microalgae hydrolysis, cellulase (New Cell Supreme 4000L) and subtilisin (a protease) (New Pro 16L), were supplied by Aquitex. The microalga was provided by Allmicroalgae-Natural Products, S.A (Pataias, Alcobaça). Sulfuric acid and Kjeldahl tablets (catalyst with 0.3% CuSO4 5H₂O) were purchased from VWR Scientific (VWR chemicals, Karlsruhe, Germany); boric acid and hydrochloric acid (32%) were purchased from Merck (Darmdstadt, Germany); sodium hydroxide was purchased from LabChem (Zelienople, PA, USA). The proteins standard used (thyroglobulin, ferritin, aldolase, conalbumin, ovalbumin, carbonic anhydrase, ribonuclease A, and aprotinin) were acquired from GE Healthcare (Milwaukee, WI, USA), and the peptide KGYGGVSLPEW was obtained from GenScript (Nanjing, China).
Regarding the bioactivities, fluorescein, 2,2′-azo-bis-(2-methylpropionamidine)-dihydrochloride (≥97%), 6-hydroxy-2,5,7,8-tetramethylbroman-2-carboxylic acid (Trolox) (≥97%), angiotensin I-converting enzyme (EC 3.4.15.1, 5.1 U mg⁻¹), and α-glucosidase (EC 3.2.1.20) were acquired from Sigma-Aldrich (St. Louis, MO, USA), while Abz–Gly–Phe (NO₂)–Pro was supplied by Bachem Feinchemikalien (Bubendorf, Switzerland).