J. Biol. Chem., Vol. 260, Issue 5, 2657-2661, 03, 1985
Inactivation of muscle adenylate kinase by site-specific destruction of tyrosine 95 using potassium ferrate
MD Crivellone, M Hermodson and B Axelrod
Potassium ferrate, an analog of orthophosphate and a potent oxidizing
agent, was found to irreversibly inactivate porcine muscle adenylate
kinase. Inhibition was prevented by competitive inhibitors or substrates,
indicating that the action of ferrate was site-specific. Inactivation was
accompanied by the loss of Cys-25 and Tyr-95. P1,P5- di(adenosine
5')-pentaphosphate (10(-7) M), a powerful competitive inhibitor, gave 50%
protection to the enzyme from ferrate inactivation. No loss of tyrosine or
cysteine residues was observed under conditions of total protection. The
degree of inactivation was proportional to the amount of Tyr-95 destroyed.
However, Cys-25 was totally oxidized when only 55% inactivation had
occurred. Partially inactivated enzyme exhibited a Km for ATP and AMP
similar to that of the untreated enzyme. It appears that Cys-25 may be
proximate to a phosphate-binding site but is not directly involved in the
catalytic reaction. The results suggest that Tyr-95 is located in the
vicinity of a phosphate-binding region of adenylate kinase and is essential
for enzyme activity.