KINETIC-STUDY OF THE REACTION OF PYRIDOXAL 5'-PHOSPHATE WITH HYDRAZINE

The kinetics of the reaction between pyridoxal 5'-phosphate (PLP) and hydrazine in aqueous solution at a variable pH and a constant strength of 0.1 M was studied spectrophotometrically. The rate constants of fo rmation and hydrolysis of the resulting Schiff base and its stability were also determined in a wide range of pH. A comparison of the format ion rate constants with those for the models of PLP with n-hexylamine and with poly-L-lysine revealed that hydrazine formed Schiff base more quickly than lysine below pH 7 and than n-hexylamine below pH 8. The reactivity shows the sequence poly-L-lysine > n-hexylamine > hydrazine in whole studied range of pH. Schiff bases formed by hydrazine with P LP are more stable than the ones formed by n-hexylamine in the pH rang e studied and more stable than the formed by poly-L-lysine at pH < 7.0 . (C) 1998 Elsevier Science B.V.