Enzymatic hydrolysates were obtained by hydrolysis of retorted skin gelatin hydrolysates (RSGH) from bullfrog (Rana catesbeiana) using three enzymes including collagenase, bromelain, and pancreatin for various times (0, 15, 30 and 60 min). As the hydrolysis time increased, degrees of hydrolysis (DH) of all three enzymatic hydrolysates increased. The molecular weight distribution of collagenase-hydrolyzed RSGH (RSGH-Cg) fraction was in the range of 189 - 686 Da (40.1 - 50.1%) and 686 - 6,511 Da (36.7 - 48.7%) while those of the other enzymatic-hydrolyzed RSGH fractions were mostly in the 686 - 6,511 Da (58.2 - 60.8%) range. All enzymatic hydrolysates had more potent antioxidant activity including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferrous
ion chelating activity, and reducing power than the original RSGH. RSGH-Cg showed the highest activity. The lower IC50 value of angiotensin I-converting enzyme (ACE) inhibitory activity of RSGH-Cg correlated with the degree of hydrolysis. This study suggested that collagenase treated bullfrog RSGH is a promising functional ingredient.