Adenylate Deaminase

Abstract

Adenylate deaminase from brain is activated by adenosine triphosphate (l-4).Early studies showed that adenylate deaminase activity is widely distributed in animal tissues (5).No evidence was presented previously that the deaminase from tissues other than brain is affected by nucleoside triphosphates.This communication reports that in addition to being activated by adenosine triphosphate, the enzyme from brain is strongly inhibited by guanosine triphosphate.A similar enzyme occurs in many other rat tissues.It is proposed that this type of adenylate deaminase is involved in regulating the relative amounts of adenine, hypoxanthine, and guanine nucleotides in the cell.The effects of adenosine and guanosine triphosphates on the enzyme from calf brain are shown in Table I.ATP causes a strong activation of the enzyme at 2 mM AMP but not at 50 n?M AMP.The effect of ATP concentration on the reaction rate follows Michaelis-Menten enzyme kinetics.The apcarent K, for ATP is 170 PM at an AMP concentration of 2 mM.GTP causes an inhibition of the enzyme both at 2 mM and 50 mM AMP.