Studies On The Silk Sericin Protein As A Support Of Immobilized L-asparaginase

L-asparaginase obtained from E.coli has been extensively used in the treatment of acute lymphoblastic leukemia. Notwithstanding its high therapeutic efficacy, the therapeutic use of asparaginase may lead to severe side effects such as fever, skin rashes, allergic reactions and even anaphylactic shocks. Furthermore, L-asparaginase circulates in the blood system for only a short time before being taken up and broken down by native proteases, which restrictedly limit its effective only to a certain degree. In order to eliminate these disadvantages, the native L-asparaginase was often chemical modified with various kinds of biocompatible polymers to produce various immobilized L-asparaginase.In this article, the silkworm cocoons or the waste silk during raw silk production at the reeling mill and the other stages of silk processing was used for materials. Under high-temperature and high-pressure conditions, the silk sericin protein aqueous solution was produed. After purifying, condensing and spray drying, we produced the hot water-soluble sericin protein powder. This kind of sericin protein, whose molecular weight is not less than 200 kDa and average size is about 12 jam, is a hot water-soluble protein which can only dissolve in the hot water of which temperture is higher than 98癈. Continued to deal with this hot water-soluble sericin protein with 0.1-3N HC1 and the solution was neutralized, filtrated, purified and sprayed dry again, we produced the other kind of sericin protein, whose molecular weight is not less than 60 kDa and easy to dissolve in cold water.In this paper, utilizing these two kinds of macromolecular sericin protein as carriers and using glutaraldehyde as the cross-linking reagent, we prepared two kinds of immobilized L-asparaginase. One is insoluble granule and the other is soluble in water.The activity and dynamical properties of these immobilized L-asparaginases were described that the immobilized enzymes were more stable than the native enzyme and keep good storage stability as well. Immobilized L-asparaginase have preferable stability of operation and Longer half-life time in vitro. In addition, the resistance to trypsin hydrolysis was improved greatly in comparison with that of native enzyme and the stabilities to heat increased obviously also.The Km of the L-asparaginase immobilized with the hot water-soluble sericin protein was 1.2 10-3mol/L, lower 12 times than the Km (1.0 10-2mol/L) of the native enzyme. The Km of the L-asparaginase immobilized with the water-soluble sericin protein was l.67 10-4mol/L, lower 60 times than the Km (1.0 10-2mol/L) of the native enzyme. It is indicated that the affinity between the immobilized L-asparaginase and its substrate asparagine was greatly increased.The final concentration of this article is that not the hot water-soluble sericin protein powder but the water-soluble sericin protein is a favorable material for immobilized L-asparaginase.