4 2 pyridinazo resorcinol par

Naked oat bran was purchased from Sanfen Oat Farm, Shuozhou, China. Trypsin (1 × 10⁴ U/g, derived from porcine pancreases), Pepsin (1 × 10⁵ U/g, derived from bovine stomachs), Flavourzyme (from Aspergillus oryzae, 2 × 10⁴ U/g), pancreatin (1 × 10⁴ U/g, derived from porcine pancreases), and Papain (3 × 10⁴ U/g) were purchased from Kangfukuai Biotech., Co. (Nanning, China). ACE, 4-(2-Pyridinazo)-resorcinol (PAR) and N-hippuryl-L-histidyl-L-leucine (HHL) were purchased from Sigma (St. Louis, MO, USA). Zinc sulfate heptahydrate (ZnSO₄·7H₂O), HEPES-KOH buffer, and other analytical grade chemicals were purchased from Jinyangkeji Co. (Taiyuan, China).

DOPK was provided by the Three Rivers Palm Garden (Haikou, China). Trypsin (1 × 10⁴ U/g, derived from porcine pancreas), papain (3 × 10⁴ U/g), and pepsin (1 × 10⁵ U/g, derived from bovine stomach) were purchased from Kangfukuai Biotechnology Co. (Nanning, China). ACE, 4-(2-Pyridinazo)-resorcinol (PAR), and N-hippuryl-l-histidyl-l-leucine (HHL) were purchased from Sigma (St. Louis, MO, United States). Dithiothreitol, HEPES-KOH buffer, and other chemicals were purchased from Jinyangkeji Co. (Linfen, China).