Study On Chemical Modification Of Enzymes By Maltose And Their Properties

Objective: Maltose was modified by oxidation method with sodium periodate, trypsin、α-amylase、lipase was modified by modified maltose. Whether this method could improve theactivities and properties of the enzymes was checked. Method: Maltose was modified withsodium periodate, in order that there was aldehyde group which could combine withamino-group of enzyme molecule in it, so it could modify trypsin、α-amylase、lipasechemically under certain conditions. After comparing modification effects, optimum pH、optimum temperature、pH stability and thermal stability of modified trypsin which retainedmore enzymatic activity was studied. Result: The optimum conditions for modifying maltosewere as follows: Concentration of sodium periodate0.05g/mL, Mass ratio of sodiumperiodate and maltose1.1:1, Initial pH1.0, Reaction time3h, Reaction temperature30℃;The optimum conditions for modifying trypsin were as follows: pH6.0, Mass ratio ofmodified maltose and trypsin1:1, Modification temperature4℃, Modification time24h,activity of trypsin retained65.8%of activity of original trypsin after modification; Theoptimum conditions for modifying α-amylase were as follows: pH8.0, Mass ratio of modifiedmaltose and α-amylase1:4, Modification temperature4℃, Modification time12h, activity ofα-amylase retained59.7%of activity of original α-amylase after modification; The optimumconditions for modifying lipase were as follows: pH8.0, Mass ratio of modified maltose andlipase1:10, Modification temperature4℃, Modification time24h, activity of lipase retained54.9%of activity of original lipase after modification; After modifying trypsin underoptimum conditions, its optimum pH(about pH9.0) and optimum temperature(about50℃) didnot change obviously comparing to original trypsin; Under different pH for2h, the activity ofmodified trypsin and original trypsin was determined, the results showed that, during therange of pH9.0~10.0, the activity of original trypsin and modified trypsin dropped15.8%and9.8%of their highest activity respectively; Under50℃for2h, the activity of original trypsinand modified trypsin retained88.7%and94.7%of their activity under4℃for2h respectively.Conclusion: After modification with this method, the activities of trypsin、α-amylase、lipaseall somewhat dropped; But from studying on modified trypsin, we knowed that after modification with this method the stabilities of trypsin for resisting alkali and heat could beimproved.