Characterization and cAMP inhibition of a lysyl-( N- ϵ-5′-phospho) adenosyl phosphoamidase in Dictyostelium discoideum

1. 1. A lysyl-( N- ϵ-5′-phospho) adenosyl phosphoamidase activity has been identified in Dictyostelium discoideum. Conjugates, formed by coupling AMP via a phosphoamide bond to the epsilon amino group of lysine in avidin and tuftsin, served as substrate. 2. 2. Lysyl- N- ϵ-5′-phosphoadenosine and adenosine phosphoramidate (AMPNH) were substrates as well. 3. 3. The phosphoamidase liberated AMP from all four compounds but did not degrade cAMP. 4. 4. Approximately 90% of the phosphoamidase activity was inhibited competitively by 100 μM cAMP with an apparent K i of 35 μM for all substrates.