title: Synthesis of model compounds relevant to the active-site-directed inactivation of L-asparaginase by 5-diazo-4-oxo-L-norvaline.
abstract: Earlier work has shown that 5-diazo-4-oxo-L-norvaline (DONV) irreversibly inactivates the L-asparaginase from E. coli by formation of a covalent bond in the region of the active site. Model compounds have been prepared to study this acid-labile covalent bond tentatively assigned to a serine or possibly a threonine residue in a decapeptide isolated from 14C-DONV-inactivated enzyme. Appropriately blocked DONV was found to alkylate methanol, and the hydroxyl function of blocked serine or threonine in the presence of boron trifluoride. The labile beta-ketoethers thus formed were reduced to the more stable beta-hydroxyethers. Facile lactonization of these 5-substituted-4-hydroxy-L-norvalines was observed. The diastereoisomers of both the lactonized and open forms of 5-methoxy-4-hydroxy-L-norvaline and related 4-hydroxy-L-2-amino acids of similar length were distinguishable on the amino acid analyzer. The beta-hydroxyethers derived from serine and threonine were hydrolyzed with acid and yielded the expected cleavage products. When the beta-ketoether was reduced by sodium borohydride prior to deblocking, in addition to the beta-hydroxyether, N-blocked amino alcohols were also formed, yielding a complex mixture of products.
mesh_terms: D000478:Alkylation; D000622:Aminolevulinic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D001215:Asparaginase / Q000378:metabolism*; D055598:Chemical Phenomena; D002621:Chemistry; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D007982:Levulinic Acids / Q000378:metabolism*; D008956:Models, Chemical
chemical_list: D007982:Levulinic Acids; D000622:Aminolevulinic Acid; D001215:Asparaginase