Substrate Binding and Intersubunit Interactions in l-Asparaginase

Abstract d-Asparagine prevents the dissociation of Escherichia colil-asparaginase. Conditions that affect the rate of hydrolysis of the substrate also influence the extent of protection. The most effective stabilization of the tetrameric aggregate is provided between pH 5 and 8 with half-maximal rates of dissociation occurring at pH 4.2 and 8.8. Partial acetylation of tyrosyl residues of l-asparaginase results in modification of behavior of the enzyme towards the protective action of d-asparagine. The results of these studies have provided an indication of the nature of the amino acid residues at the substrate-binding site.