Functional development of porcine spleen as a by-product of pig slaughterhouse: Preparation, identification and bioactive activities of a novel peptide

Abstract

Porcine spleen, by-product of pig slaughterhouses, was often threw away due to underutilization, resulting in the neglect of the development of high-quality active materials. In this study, water-soluble porcine spleen peptide (w-PSP) was prepared by enzymatic hydrolysis. It was a mixed peptide with a molecular weight of less than 3000 Da and contained 7097 short peptides consisting of 5–15 amino acids residues. The w-PSP contained 65.33% hydrophilic amino acids. β-sheet was the main secondary structure conformation in w-PSP. The activity verification experiments confirmed that w-PSP presented no antitumor activity in vitro and in vivo. But it exhibited conspicuous antioxidant properties. The maximum scavenging rates of w-PSP to 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals were 78.19% and 75.53%, respectively. Anti-superoxide anion (O2-) radical activity and anti-hydroxyl (OH) radical activity of w-PSP reached 94.19 U/L and 396.40 U/mL. Besides, the activities of glutathione peroxidase (GSH-PX) in liver, spleen, kidney and serum of w-PSP treated mice were significantly increased to 266.82 mgGSH/gprot, 226.37 mgGSH/gprot, 239.03 mgGSH/gprot and 1376.38 mgGSH/L. The activities of superoxide dismutase (SOD) in liver, spleen, kidney and serum of w-PSP treated mice were increased to 1614.66 U/mgprot, 1614.51 U/mgprot, 677.11 U/mgprot and 156.91 U/mL. The malondialdehyde (MDA) contents in w-PSP treatment groups were obviously decreased. De novo sequencing and bioinformatics prediction were used to identify and analyze peptides in w-PSP. Good molecular docking results suggested the antioxidant mechanism of w-PSP might be related to the Keap1-Nrf2 signaling pathway.