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 (Raja clavata) muscle hydrolysed with Bacillus subtilis A26 proteases until a hydrolysis degree of 18.35%. The hydrolysate showed an IC50 of 0.83mgmL(-1). To identify peptides responsible for this activity, the extract was eluted through size-exclusion chromatography and fractions collected. The highest ACE inhibitory activity was found for fractions F2 and F3 which had IC50 of 0.42 and 0.51mgmL(-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 chain and procollagen alpha 1 chain proteins were identified in fractions F2 and F3, respectively. FQPSF and LKYPI showed the best results with an IC50 of 12.56 and 27.07M, respectively. These results prove the potential of thornback ray muscle hydrolysate as a source of ACE inhibitory peptides.