Synthesis, physicochemical and immunological properties of oxidized inulin-L-asparaginase bioconjugate

In recent years several bioconjugation protocols have been developed to improve the pharmacokinetic and immunological properties of anti-leukemic enzyme, L-asparaginase. In this study we investigated the effect of conjugation with oxidized inulin on these properties. Inulin (MW about 25 kDa) was oxidized with periodate and was conjugated to the enzyme at molar ratios of oxidized inulin to enzyme between 2:1 and 4:1. Modified L-asparaginase synthesized at ratio of 2:1 had activity of 65% of that of native enzyme and was used in subsequent experiments. The apparent K-m of glycoconjugate (0.1 x 10(-4) M) was about five times lower than the K-m of native enzyme (0.57 x 10(-4) M). Modified L-asparaginase had longer half life, higher thermostability and more resistance to trypsin digestion and better reusability after repeated freezing and wider optimum pH range than that of intact L-asparaginase. The modification of L-asparaginase with oxidized inulin at molar ratio of 2:1 resulted in decreasing antibody (IgG) titer and immunogenecity after repeated injection of rabbits with respect to the native L-asparaginase. Taken together, the results of this Study indicated that L-asparaginase modification by oxidized inulin results in a new stabilized product with improved biochemical properties which may be employed for medical purposes. (C) 2009 Elsevier B.V. All rights reserved.