Inhibition of dihydroxyphenylalanine decarboxylase by derivatives of phenylalanine

A series of compounds, related chemically to phenylalanine, have been examined for their action on dopa decarboxylase of pig kidney and on bacterial tyrosine decar boxylase, and some of the compounds were found to inhibit these enzymes.

Abstract

A series of compounds, related chemically to phenylalanine, have been examined for their action on dopa decarboxylase of pig kidney and on bacterial tyrosine decarboxylase. Some of the compounds were found to inhibit these enzymes. The relation between degree of inhibition and chemical structure of the inhibitors has been discussed. Generally, those compounds which inhibited had a more marked effect on the kidney enzyme than on the bacterial enzyme. Two compounds, α-methyl-3,4-dopa (α-MD) and α-methyl-3-hydroxyphenylalanine, respectively, added in a low range of concentrations, accelerated, and at higher concentrations, inhibited, kidney dopa decarboxylase. The mechanism of this biphasic action has been examined experimentally. Substrate inhibition of dopa decarboxylase by 2,5- and 2,4-dopa has been observed.