The Effects Of Acid Chloride Modification On The Biological Properties Of L-Asparaginases With Antilymphoma Activity

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Microbiology and Immunology


In this study, we have developed a drug delivery system which is a systematic approach to the soluble chemical modification of antigenic proteins. Increasing chain length acid chlorides have been reacted with L-asparaginase for specified times.The acylation of asparaginase with short-chain-length acid chlorides such as acetyl chloride and trimethylacetyl chloride have produced molecules with extended half-lives, reductions in antigenicity and superior antitumor activity as compared to the native enzymes. Erwinia carotovora asparaginase acylated with butyryl chloride has an extension in half-life compared to the native enzyme but has equivalent antigenicity and slightly superior antitumor activity. Escherichia coli asparaginase acylated with butyryl chloride has an extended half-life as well as antitumor activity equivalent to the native enzyme. The acylation of E. carotovora asparaginase with hexanoyl chloride has resulted in the enzyme having an extension in half-life, reduced antigenicity and superior antitumor activity than the native enzyme. E. coli asparaginase acylated with hexanoyl chloride has a half-life which is slightly greater than the native enzyme. The acylation of E. carotovora and E. coli asparaginase with decanoyl chloride resulted in the enzymes having half-lives equivalent to their respective enzymes.Superior antitumor activity was observed with asparaginases that had extensions in biological half-life compared to the native enzyme. The superior antitumor activity was not solely a result of the half-life because enzymes modified with different acid chlorides and equivalent extensions in half-life had varying antitumor activity.The reductions in antigenicity correlated with the percentage of free amino groups bound by a single acid chloride. There was no correlation between the percentage of free amino groups bound and decrease in antigenicity between the various acid chlorides employed.We have employed the enzyme L-asparaginase, isolated from E. coli and E. carotovora, as the prototype for a modification procedure which involves the systematic addition of increasingly longer chain length acid chlorides. Our modifications have resulted in proteins having superior biological activity as compared to their native counterparts depending upon the chain length of the acid chloride employed as well as the extent of modification. We feel that this modification scheme can be used with other proteins to produce desired improvements in biological activity. (Abstract shortened with permission of author.)


Biology, Microbiology

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