Chemical Modification of L-Asparaginase from Cladosporium Sp. for Improved Activity and Thermal Stability.

L-Asparaginase (ASNase), an antileukemia enzyme, is facing problems with antigenicity in the
blood. Modification of L-asparaginase from Cladosporium sp. was tried to obtain improved
stability and improved functionality. In our experiment, modification of the enzyme was tried with
bovine serum albumin, ovalbumin by crosslinking using glutaraldehyde, N-bromosuccinimide, and
mono-methoxy polyethylene glycol. Modified enzymes were studied for activity, temperature stability,
rate constants (kd), and protection to proteolytic digestion. Modification with ovalbumin resulted in
improved enzyme activity that was 10-fold higher compared to native enzyme, while modification
with bovine serum albumin through glutaraldehyde cross-linking resulted in high stability of
L-asparaginase that was 8.5- and 7.62-fold more compared to native enzyme at 28�C and 37�C
by the end of 24 hr. These effects were dependent on the quantity of conjugate formed. Modification
also markedly prolonged L-asparaginase half-life and serum stability. N-Bromosuccinimidemodified
ASNase presented greater stability with prolonged in vitro half-life of 144 hr to proteolytic
digestion relative to unmodified enzyme (93 h). The present work could be seen as producing a
modified L-asparaginase with improved activity and stability and can be a potential source for
developing therapeutic agents for cancer treatment.