Fhit proteins can also recognize substrates other than dinucleoside polyphosphates

We show here that Fhit proteins, in addition to their function as dinucleoside triphosphate hydrolases, act similarly to adenylylsulfatases and nucleoside phosphoramidases, liberating nucleoside 5′-monophosphates from such natural metabolites as adenosine 5′-phosphosulfate and adenosine 5′-phosphoramidate. Moreover, Fhits recognize synthetic nucleotides, such as adenosine 5′-O-phosphorofluoridate and adenosine 5′-O-(γ-fluorotriphosphate), and release AMP from them. With respect to the former, Fhits behave like a phosphodiesterase I concomitant with cleavage of the P–F bond. Some kinetic parameters and implications of the novel reactions catalyzed by the human and plant (Arabidopsis thaliana) Fhit proteins are presented.