DETERMINATION OF THE RATES OF FORMATION AND HYDROLYSIS OF THE SCHIFF-BASES FORMED BY 5'-DEOXYPYRIDOXAL AND POLY-L-LYSINE

The kinetics of the reaction between 5'-deoxypyridoxal (DPL) and poly- L-lysine in aqueous solutions at a variable pH and a constant ionic st rength of 0.1 M was studied spectrophotometrically. The rate constants of formation and hydrolysis of the resulting Schiff base and its stab ility constant at a variable pH were also determined. A comparison of the formation rate constant for the Schiff base with those for the mod els of pyridoxal 5'-phosphate (PLP) with poly-L-lysine and DPL with n- hexylamine revealed the effect of both the phosphate group of PLP and of the polypeptide chain on intramolecular catalysis in the dehydratio n of the intermediate carbinolamine formed. The effects of the polypep tide and the phosphate group on the hydrolysis of the Schiff base and hence on the base stability are also demonstrated.