Novel potential XOD inhibitory peptides derived from Trachinotus ovatus: Isolation, identification and structure-function analysis

This study aimed to isolate and identify the novel potential Xanthine oxidase (XOD) inhibitory peptides derived from Trachinotus ovatus hydrolysate (TOH) (hydrolysis by neutral protease), and investigate their structure-function relationship. Initially, TOH was separated to four fractions (F1-F4) by gel filtration chromatography and F4 was chosen with higher XOD inhibitory rate (85.16% & PLUSMN; 0.566, 25 mg/mL) and lower molecular weight (95.73%, < 1000 Da). F4 was further characterized by reversed-phase high performance liquid chromatography (RP-HPLC) coupled with Nano-HPLC-MS/MS and four peptides (FPAW, LLPW, WLLP and FHLP) were identified with IC50 value of 3.81 & PLUSMN; 0.18 mM, 4.17 & PLUSMN; 0.12 mM, 43.06 & PLUSMN; 0.73 mM, and over 50.00 mM respectively. It can be concluded that Trp-containing peptides especially located in C-terminal could inhibit XOD effectively. Moreover, the XOD-inhibiting actions of these peptides involved pi-pi stacking (Phe914 and Phe1009 in XOD), hydrogen bonding via molecular docking. Lineweaver-Burk equation showed the inhibition type of FPAW was a mixed inhibition. Circular dichroism (CD) spectra indicated FPAW could combine and change the secondary structure of XOD. Therefore, two peptides of FPAW and LLPW might have potential to be used to alleviate hyperuricemia in the future.