Angiotensin I‐converting enzyme inhibitory peptides FQPSF and LKYPI identified in Bacillus subtilis A26 hydrolysate of thornback ray muscle.

Angiotensin I-converting enzyme (ACE) inhibitory peptides have been searched in thornback ray (Rajaclavata) muscle hydrolysed with Bacillus subtilis A26 proteases until a hydrolysis degree of 18.35%. Thehydrolysate showed an IC50of 0.83 mg mL1. To identify peptides responsible for this activity, theextract was eluted through size-exclusion chromatography and fractions collected. The highest ACE inhi-bitory activity was found for fractions F2 and F3 which had IC50of 0.42 and 0.51 mg mL1, respectively.These fractions were analysed by nano-liquid chromatography coupled to tandem mass spectrometry(nLC-MS/MS). A total of 131 and 108 peptide sequences mainly derived from actin, myosin heavy chainand procollagen alpha 1 chain proteins were identified in fractions F2 and F3, respectively. FQPSF andLKYPI showed the best results with an IC50of 12.56 and 27.07 lM, respectively. These results prove thepotential of thornback ray muscle hydrolysate as a source of ACE inhibitory peptides.