Factors Influencing the Rate of Non-Enzymatic Activation of Carboxylic and Amino Acids by ATP

Abstract

The rate of non-enzymatic activation of carboxylic and amino acids by ATP has been found to vary as a function of several factors. These include, (a) the pK_a of the carboxyl group, (b) pH, (c) temperature, (d) salt concentration, (e) the divalent metal cation, (f) the molar ratio of metal cation to ATP, and (g) the nature of the amino acid. The rates of activation of a select group of hydrophobic amino acids (phe, leu, val, ile and met) were found to differ under a variety of conditions, although phe was always activated most rapidly. This amino acid, moreover, was always found to have the greatest affinity for various adenine derivatives as determined by several methods. We conclude that the rate of non-enzymatic activation of amino acids by ATP is at least partially a function of the affinity of the amino acid for this nucleotide.