Effect of suramin on phosphorylation-dephosphorylation reactions in Trypanosoma gambiense

Suramin which is used as a chemotherapeutic agent against sleeping sickness was tested for its ability to inhibit phosphorylation-dephosphorylation reactions in Trypanosoma gambiense. Protein-kinase I, which is characterized by its preference for acidic acceptor proteins, was found to be strongly inhibited by suramin. The inhibition constant was calculated to be 0.8 microM. The type of inhibition was non-competitive with respect to ATP as well as to substrate protein.