Isolation of a novel peptide from silkworm pupae protein components and interaction characteristics to angiotensin I-converting enzyme

The hydrolysate of silkworm protein produced by acid protease (Asperqiius usamii NO. 537) contains angiotensin I-converting enzyme inhibitory activity. Four kinds of protein components were identified in silkworm pupae protein, albumin, globulin, prolamin and glutelin, and the albumin was in the highest quantity. The four component proteins were then further hydrolyzed by acid protease under the same conditions, and the hydrolysate of albumin was determined with the highest ACE inhibiting effect, followed by globulin. Albumin could be easily hydrolyzed under the aqueous conditions, and the overall albumin protein content was higher than the other three protein components. The peptide sequence APPPKK'' was determined by LC-MS/MS separation and X!Tandem software identification. The peptide inhibitory activity was 0.047 mg/mL in IC50. The peptide was bonded to Asp(415), Asp(453), Thr(282), His(353), Glu(162) in hydrogen bond to ACE active pocket by flexible docking calculations. This study indicates that silkworm pupae protein may be a suitable candidate to explore functional foods with anti-hypertension bioactivity.