Isolation,Purification And Properties,Modification Of Groups Of ?-glucosidase From Leaf Skin Of Aloe Vera

?-Glucosidases(?-D-glucopyranoside glucohydrolases,E.C.3.2.1.21)are found in all domains of living organisms,where they play essential roles in the removal of nonreducing terminal glucosyl residues from glucoconjugates,including glucosides,1-O-glucosyl esters,and oligosaccharides.It has a wide range of functions in plants,animals and microorganisms,including lignification,catabolism of cellwall oligosaccharides,defense,phytohormone conjugate activation,release ofaromatic compounds,as well as both sidesof plant-microbe and plant-insect interactions,breakdown of glycolipids and exogenous glucosides in animals,and biomass conversion in microorganisms.These functions lead to many food,agricultural and energy resources applications.Especially in food scent,?-Glucosidases promotes the aroma effect of alcohol,fruit juice and tea,and combines with glycoside spice precursors asnatural flavor to provide new areas for new natural flavors.It is in plants that ?-glucosidases have been found to play the widest array of biological functions.Aloe vera is widely planted and has developed rapidly in food,medicine and cosmetic because of its abundant nutritional value and health care value.As the mian byproduct of processing,leaf skin of Aloe vera is discarded.In this study,we carried out a research on the isolation,purification,properties and functional groups of ?-Glucosidase from leaf skin of Aloe vera,in order to provide a new way for obtaining ?-Glucosidase and effectively reduce resource waste and environmental pollution,which provides a theoretical basis for further study of natural flavor and other application functions.1.Isolation and Purification of ?-Glucosidase from leaf skin of Aloe vera Electrophoresis-purity ?-Glucosidase from the fresh leaf skin of Aloe vera was obtained through the procedures of citrate buffer homogenization and extraction,ammonium sulfate precipitation and dialysis,DEAE-Sepharose fast flow chromatography and Superdex-200 prep grade chromatography.9.87%of the?-Glucosidase activity was obtained,the purification fold was 328.27,the specific activity was 98.48 U/mg.2.Characteristics of ?-Glucosidase from leaf skin of Aloe veraThe molecular weight of ?-Glucosidase was approximately 69.7 kD,in which the subunit molecular mass was roughly 69.3 kD,which indicated that the enzyme is composed of single subunit.Characterization results show that the optimum pH and temperature of ?-Glucosidase were 5.0 and 40?,respectively.It was stable relatively in the range of pH 5.0-8.0 and 20-30?,respectively,with a strong acid alkali tolerance.Its Km and Vmax were 2.21 mmol/L and 1.381 ?mol/min·L towards pNPG,respectively.3.Effects of different metal ions,compounds and organic solvents on the activity of ?-Glucosidase from leaf skin of Aloe vera.The activity of ?-Glucosidase could be activated by ethanol,ascorbic acid,Mn2+,K+,and strongly inhibited by SDS,Cu2+,Cd2+,Co2+,Ba2+,Ca2+ showed weak inhibitory effect.Methanol,EDTA,Zn2+ has the dual role of this enzyme.Isopropanol,urea,oxalic acid,Mg2+ and Li+ had little activation for it.4.Chemical Modification of ?-Glucosidase from leaf skin of Aloe veraModified by groups of different chemical modification agent on the function of?-Glucosidase from leaf skin of Aloe vera results showed that methionine,tryptophan resides were the essential function groups of the enzyme activity center;arginine guanidine,lysine,histidine,tyrosine,cysteine sulfhydryl resides and two disulfide bondshas no direct relationship with ?-Glucosidase activity center,so they were not the essential function groups of the enzyme.