Characterization and purification of β−secretase inhibitory peptides fraction from sea cucumber (Holothuria spinifera) enzymatic hydrolysates

Abstract

Alzheimer’s disease (AD) is widely known as a progressive neurodegenerative disorder, mainly found in the elderly population. Progressive neurodegeneration in AD can lead to cognitive functional and behavioral alterations, thus affecting public health. Based on the amyloid cascade hypothesis, enzymatic cleavage of amyloid precursor protein (APP) by β-secretase and the formation of amyloid-beta (Aβ) peptides lead to neuron cell degradation. In this study, we focused on this hypothesis and investigated bioactivities of dried Holothuria spinifera enzymatic hydrolysates. Dried H. spinifera contained 79.77 % protein with glycine being the most abundant amino acid (178.89 g/kg). Trypsin hydrolysate of H. spinifera exhibited the highest β-secretase inhibitory activity with an IC50 value of 81.94 μg/mL. RP-HPLC produced an active fraction (HPLC-F3) containing four bioactive peptides (YPIEHGIVTNWDDM*EK, IEELEEEIEAER, EYVEETTGDEYVSLK, YPIEHGIVTNWDDMEK). The predominant peptide presented in HPLC-F3 was IEELEEEIEAER. Effects of HPLC-F3 against SH-SY5Y neuroblastoma cells were tested. HPLC-F3 reduced cellular levels of β-secretase enzyme, Aβ, and soluble amyloid precursor protein beta (sAPPβ) proteins. HPLC-F3 also protected SH-SY5Y cells from oxidative stress by decreasing phosphorylation of c-Jun N-terminal kinases and p38 mitogen-activated protein kinases. Results of this study suggest that H. spinifera is a potential source for functional foods and biomedicine industries.