The extremely heat-stable 5¢-methylthioadenosine phos-phorylase from the hyperthermophilic archaeonPyrococcus furiosuswas cloned, expressed to high levels inEscherichia coli, and purified to homogeneity by heat precipitation and affinity chromatography. The recombinant enzyme was subjected to a kinetic analysis including initial velocity and product inhibition studies. The reaction follows an ordered Bi–Bi mechanism and phosphate binding precedes nucleo-side binding in the phosphorolytic direction
