Abstract: Reducing proteins were separated from Prinsepiautilis Roylefruit and the excellent biochemical properties were investigated.Improved reducing power evaluation method with Potassium Ferricyanide was used. P.utilis fruit proteins were extracted and purified by acid dissolution and ethanol precipitation.Because of the strongest reducing power of P.utilis fruit special protein 4,SDS-PAGE,amino acids automatic analysis,infrared spectroscopy,circular dichroism spectroscopy and differential scanning calorimeter were applied to determine composition,purity,molecular size,secondary structure,denaturation temperature and other biochemical characteristics of amino acids in P.utilis fruit special protein 4,respectively.The reducing power of  P.utilis fruit special protein 4 precipitated by 75% ethanol was observed.Its half effective concentration of reducing power was 24.7 mg/mL.The extracted P.utilis fruit special protein 4 presented as three distinct bands by SDS-PAGE,and the relative molecular mass were 11,14 and 34 KDa respectively.The denatured temperature of P.utilis fruit special protein 4 was 69.83 ℃.The secondary structure of P.utilis fruit special protein 4 was primarily presented as β-sheet (43.1%) and the random structure (27.6%),whereas alpha-helix (5.2%) occupies the minority.Research showed that the representative of P.utilis fruit special protein 4 was composed of several peptide chains, β-sheet in a dominant position,higher thermal denaturation temperature.These were important biochemical characteristics. P.utilis fruit special protein 4 with reducing capability was revealed as potential functional substances with excellent characteristics.

Key words: Prinsepiautilis Royle Fruit Special Protein 4, reducibility, infrared spectroscopy, secondary structure, denatured temperature