Chemical modification of E. coli L ‐asparaginase with polyethylene glycol grafted vinylpyrrolidone–maleic anhydride copolymer

Polymer–protein conjugates: an enzymatic activity perspective

“…For both proteins, enzymatic activity was higher for PM 100 than for PM 13 or MPEG 2 (Table 1). Interestingly, and in contrast to the results of Ma and co-workers, 89,90 the conjugates had greater stability towards heat and denaturing conditions, and this as a function of polymer molecular weight. This result may perhaps stem from the shorter combs (i.e., 1.5-2 kDa) in PM 13 and PM 100 compared to the 5 kDa combs on the polymers of Ma and co-workers, which may have led to greater multi-point attachment.…”

“…On the other, this process can, over time, dramatically reduce the molecular weight of the polymer, especially when the side-groups have large molecular weights. This holds particularly true for comb-type polymers which possess large side-chains such as those employed by Qian et al 89 and Lele et al 53 (5 and 1.1 kDa, respectively). Clearly, the amide and ester groups present on typical (meth)acrylate or (meth)acrylamide polymers are expected to be quite stable during the life span of the conjugate and thus should not affect the activity of the conjugate over this period.…”

Immobilization ofl-Asparaginase on Carrier Materials: A Comprehensive Review

“…A similar work was reported for immobilized L-ASNase on polyethylene glycol grafted vinylpyrrolidone–maleic anhydride (PEG- g -P­(VMP)) copolymer by Qian et al The goal of the study was to decrease the antigenicity and to improve the half-time of the L-ASNase in serum. First, PEG- g -P­(VMP) copolymer was synthesized via radical copolymerization.…”

Thiol-maleimide poly(ethylene glycol) crosslinking of L-asparaginase subunits at recombinant cysteine residues introduced by mutagenesis

“…We presume that the covalent crosslinking maintains the subunits within high proximity between each other, hereby facilitating the formation of the active tetrameric-structure triggered by the presence of the L-Asn substrate [ 63 , 64 ], a process that usually is rate limiting. To support these observations, we compared the catalytic activity of the 5kDa-PEG-conjugate and native non-modified enzyme at below biological temperature to introduce an energetic effect that should delay the association of the tetrameric-structure thus reducing the average catalytic activity as well [ 17 , 40 , 64 ]. At 24°C the native L-asparaginase exhibited a catalysis of 47.2 ± 1.7 U/mg, 30% of the one observed at 37°C.…”