Abstract:Aminopeptidase which was isolated from Bacillus subtilis was purified by ammonium sulfate precipitation and ultrafiltration using of a 30 kDa MWCO polyether sulfone(PES) membrane.Succinic anhydride(SA) was used as a modifier for the chemical modification of the purified Aminopeptidase.The effects of modification were characterized using the 6-trinitrobenzene sulfonic acid method,ultraviolet spectroscopy,and CD spectroscopy.The results showed the structure of native and modified Aminopeptidase is different.The average amino modification yield of the modified Aminopeptidase was 55.86% and the enzymatic acticity increased to 105.81%.Compared with the native Aminopeptidase,the modified Aminopeptidase exhibited apparently higher thermal stability.The Km of the modified Aminopeptidase(Km =0.75 mmol/L) was lower than native Aminopeptidase(Km =1.0 mmol/L).The result indicated that the chemical modification of Aminopeptidase increased the affinity.In addition,enzyme properties have been changed after modification.
