On the L-DOPA and carbidopa reactivity against pyridoxal 5′-phosphate.: A kinetic study
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Date
2002
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Abstract
The apparent rate constants of the formation (k(1))) and hydrolysis (k(2)) of Schiff bases formed by pyridoxal 5'-phosphate (PLP) with L-3,4-dihydroxyphenylalanine (L-DOPA) at a variable pH, 25 degreesC and an ionic strength of 0. 1 M was determined. The individual rate constants for the formation and hydrolysis of Schiff bases corresponding to the different chemical species present in the medium as a function of its acidity were also determined, as were the pK(a) values for the Schiff bases. The formation and hydrolysis rate constants of the Schiff bases were compared with those of the reaction of PLP with carbidopa (CD), showing that the reactivity Of L-DOPA and carbidopa on PLP are the same over the whole pH range studied, and that the hydrolysis rate is somewhat greater for the Schiff bases between PLP and CD than those between PLP and L-DOPA.