Purification and characterisation of a homogenised protein from Red Deer ( <i>Cervus elaphus</i> ) abomasum as a potential hyaluronidase inhibitor

Abstract To improve the utilisation of abomasum and explore the material basis of its antioxidant and hyaluronidase inhibitory activities, a homogeneous protein RDA4-1 was isolated from the abomasum of cultured red deer by two-step chromatography process for the first time in this study. It has a molecular weight of 15 kDa and comprises 43.56% essential amino acids. RDA4-1 scavenged 50.97% of DPPH• and 88.37% of ABTS+· at 1.5 mg mL−1, and inhibited hyaluronidase by 79.23% at 1 mg mL−1. The CD and fluorescence spectroscopy was used to initiate explore the hyaluronidase inhibition reaction process. With an increase in the concentration of RDA4-1 in the inhibition reaction, the wavelength of the negative peak of CD shifted from 208 to 218 nm, and the absorption of the positive peak of CD increased from 0.5 to 8.3 mdeg. Furthermore, fluorescence absorption at a wavelength of 340 nm rose from 248 to 762 au. These findings suggest that the interaction of RDA4-1 with hyaluronidase induces alterations in the secondary structure of the protein complex, and RDA4-1 binds reversibly to the enzyme in a non-covalent manner. The results of this study indicate that RDA4-1 could serve as a potential hyaluronidase inhibitor in the development of nutraceuticals.