The Reaction of Glutamate Dehydrogenase with 4‐Iodoacetamido Salicylic Acid

Abstract

1 4-Iodoacetamido salicylic acid is an irreversible inhibitor of ox liver glutamate dehydrogenase. 2 The rate of this inactivation is analysed in terms of a preliminary reversible formation of an enzyme/inhibitor complex. 3 Absorption and fluorescence spectral measurements give a 1:1 equivalence of modification and inactivation. 4 α-Oxoglutarate protects against this inactivation and this was used to derive a binding constant of 4.3 mM for this substrate in the absence of coenzyme. 5 The rate at which the response of the enzyme to the allosteric inhibitor GTP is lost is greater than the rate of loss of activity. This was used to provide information about the nature of the subunit interactions in the enzyme. 6 The response of glutamate dehydrogenase to the activator ADP is not affected by inactivation.