Human serum albumin (HSA) is widely used in clinical and cell culture applications. Conventional production of HSA from human blood is limited by the availability of blood donation and the high risk of viral transmission from donors. Here, we report the production of Oryza sativa recombinant HSA (OsrHSA) from transgenic rice seeds. The level of OsrHSA reached 10.58% of the total soluble protein of the rice grain. Large-scale production of OsrHSA generated protein with a purity >99% and a productivity rate of 2.75 g/kg brown rice. Physical and biochemical characterization of OsrHSA revealed it to be equivalent to plasma-derived HSA (pHSA). The efficiency of OsrHSA in promoting cell growth and treating liver cirrhosis in rats was similar to that of pHSA. Furthermore, OsrHSA displays similar in vitro and in vivo immunogenicity as pHSA. Our results suggest that a rice seed bioreactor produces cost-effective recombinant HSA that is safe and can help to satisfy an increasing worldwide demand for human serum albumin.

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Puerarin is a widely used compound in Chinese traditional medicine and exhibits many pharmacological activities. Binding of puerarin to human serum albumin (HSA) was investigated by ultraviolet absorbance, fluorescence, circular dichroism and molecular docking. Puerarin caused a static quenching of intrinsic fluorescence of HSA, the quenching data was analyzed by Stern-Volmer equation. There was one primary puerarin binding site on HSA with a binding constant of 4.12 x 10(4) M(-1) at 298 K. Thermodynamic analysis by Van Hoff equation found enthalpy change (DeltaH(0)) and entropy change (DeltaS(0)) were -28.01 kJ/mol and -5.63 J/mol K respectively, which indicated the hydrogen bond and Van der Waas interaction were the predominant forces in the binding process. Competitive experiments showed a displacement of warfarin by puerarin, which revealed that the binding site was located at the drug site I. Puerarin was about 2.22 nm far from the tryptophan according to the observed fluorescence resonance energy transfer between HSA and puerarin. Molecular docking suggested the hydrophobic residues such as tyrosine (Tyr) 150, Tyr 148, Tyr 149 and polar residues such as lysine (Lys) 199, Lys 195, arginine 257 and histidine 242 played an important role in the binding reaction.