ALKYLATION OF ADENOSINE DEAMINASE BY BENZYLBROMOACETATE AND 9-(PARA-BROMOACETAMIDOBENZYL)ADENINE

Adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) from calf intestinal mucosa is not affected at pH 8 by haloacetate and haloacetamide, while benzylbromoacetate and 9-(p-bromoacetamidobenzyl)adenine inactivate the enzyme. Substrate analogs protect against inactivation by these reagents. 2. 2. One mole of reagent is bound per mole of inactivated enzyme. The alkylated amino acid has been identified as lysine. 3. 3. The reaction of alkylation consists of two stages: binding of the alkylating agent (fast reaction) and alkylation of the ε-amino group of lysine (slow reaction). 4. 4. Bromoacetate, which does not inactivate the enzyme, does not alkylate the reactive lysine. 5. 5. The difference in reactivity is explained on the basis of a selectivity of the alkylation site on the enzyme towards the alkylating reagents