Characterization of the inhibition of rabbit muscle adenylate kinase by fluoride and beryllium ions

In the presence of NaF, BeCl2, ADP, and Mg2+, rabbit muscle adenylate kinase was strongly inhibited. Molecules responsible for the inhibition were identified after subjecting the inhibited enzyme to filtration-centrifugation through small Sephadex G-50 columns. Full inhibition was correlated with the entrapment of 2 mol of ADP, 1 mol of beryllium, and 1 mol of magnesium per mole of enzyme; when an excess of AMP was present together with ADP, only 1 mol of bound ADP was detected in the desalted inhibited enzyme, due to the release of a loosely bound AMP. The fluorometal species identified in the ADP-fluoroberyllate entrapped complex were BeF+, BeF2, and BeF3-. When inhibited adenylate kinase was diluted in a medium deprived of the inhibitory species, the enzyme activity was progressively recovered, and a k(off) value of 0.23 min-1 for the release of the inhibitor complex was calculated. The possibility that the inhibitory nucleotide-fluoroberyllate complex behaves as a transition-state analog is discussed.