Abstract
Summary
DOPA decarboxylation occurred enzymatically and nonenzymatically. In the absence of tissue the reaction proceeded nonenzymatically. In the presence of liver tissue an enzymatic reaction took place while the nonenzymatic reaction appeared to be inhibited by a dialyzable compound in the liver homogenate. The enzymatic decarboxylation of DOPA was extremely slow when compared with similar preparations from animal tissues. The pH optimum was between 7 and 8. The reaction was inhibited by p-chloromercuribenzoate, dopamine, 5-hydroxytryptamine, and competitively by 5-hydroxytryptophan. Phenylpyruvic acid strongly inhibited the reaction in homogenates of livers obtained at two autopsies but proved to be a weaker inhibitor in the case of homogenates of liver obtained at two other autopsies. Norepinephrine, EDTA. chlorpromazine, α-methyl DOPA and phenylalanine did not markedly influence the enzymatic DOPA decarboxylation.
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