title: Kinetic and thermodynamic parameters for Schiff base formation of vitamin B6 derivatives with amino acids.
abstract: Thermodynamic and kinetic parameters for Schiff base formation of pyridoxal 5'-phosphate and pyridoxal with epsilon-aminocaproic acid as well as of pyridoxal 5'-phosphate with L-serine were obtained in 0.1 M sodium pyrophosphate buffer as a function of temperature. Changes in enthalpy, which were determined by direct microcalorimetry, were small at 25 degrees C, but varied strongly with pH for the reaction of pyridoxal 5'-phosphate with the amino acids. In contrast to the fast Schiff base formation of pyridoxal 5'-phosphate, a very slow reaction was found for pyridoxal and epsilon-aminocaproic acid concomitant with a larger change in enthalpy. By preventing hemiacetal formation the phosphate moiety plays a crucial role.
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D015119:Aminocaproic Acid / Q000378:metabolism; D007700:Kinetics; D011730:Pyridoxal / Q000378:metabolism; D011732:Pyridoxal Phosphate / Q000378:metabolism; D011736:Pyridoxine / Q000378:metabolism*; D012545:Schiff Bases / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D012545:Schiff Bases; D011730:Pyridoxal; D012694:Serine; D011732:Pyridoxal Phosphate; D011736:Pyridoxine; D015119:Aminocaproic Acid