Gr. Echevarria et al., PHOTOPHYSICAL STUDY OF PYRIDOXAL 5'-PHOSPHATE AND ITS SCHIFF-BASE WITH N-HEXYLAMINE, Photochemistry and photobiology, 66(6), 1997, pp. 810-816
Phosphopyridoxal enzymes exhibit a wide variety of reactions, The acti
vation mechanism proceeds with the formation of Schiff bases that unde
rgo loss or transfer of one or more protons. Changes in the fluorescen
t properties of the pyridoxal 5'-phosphate and its Schiff base may sig
nal changes in the protonation state and/or in the microenvironment of
the cofactor. In this paper the average fluorescence lifetime of pyri
doxal 5'-phosphate (PLP) as a function of pH was studied in a medium o
f 0.1 M ionic strength at 25 degrees C. The ionic species of PLP with
an unprotonated hydrogen atom were found to exhibit fluorescence lifet
imes in the region of 100 ps on excitation at lambda = 390 nm. The ave
rage fluorescence lifetimes for PLP in its Schiff bases with n-hexylam
ine in media of low polarity are reported.