COMPETITIVE INHIBITION OF 3, 4-DIHYDROXYPHENYLALANINE (DOPA) DECARBOXYLASE IN VITRO

Reactions of DOPA (3,4-dihydroxyphenylalanine) decarboxylase with DOPA.

The study of DOPA (3,4-dihydroxyphenylalanine) decarboxylase by steady-state methods is difficult because multiple reactions occur. The reaction with DOPA was studied at enzyme concentrations between 20 and 50 micrometer by direct observation of the bound coenzyme by using stopped-flow and conventional spectrophotometry. Four processes were observed on different time scales and three of these w...

Inhibition of DOPA decarboxylase in vitro and in vivo.

3,4-Dihydroxyphenylalanine (dopa) decarboxylase activity in the arthropod nervous system.

1. When homogenates of brains from mature adult locusts (Locusta migratoria) were incubated with l-3-(3,4-dihydroxyphenyl)[3-(14)C]alanine the major radioactive metabolite was dopamine, suggesting the presence of a dopa (3,4-dihydroxyphenylalanine) decarboxylase. 2. Decarboxylation of l-dopa by this tissue, measured under optimum conditions by a radiochemical method, was 21mumol of CO(2)/h per ...

Decrease of the 3,4-dihydroxyphenylalanine (DOPA) decarboxylase activities in human erythrocytes and mouse tissues after administration of DOPA.

Human erythrocytes have been found to contain appreciable amounts of DOPA decarboxylase (EC 4.1.1.26) activity. The enzyme activity in erythrocytes from patients with Parkinson's disease who were treated with DOPA was significantly lower than that of untreated patients and of normal individuals. Administration of the drug to mice led to a marked decrease of DOPA decarboxylase in liver and kidne...

DOPA decarboxylase inhibition through the interaction of coenzyme and substrate.

The method of &hales and Schales (1) for obtaining a stable preparation of 3,4-dihydroxyphenyl-n-alanine (L-dopa) decarboxylase has simplified the problem of studying the kinetics of this enzyme system. These authors studied the effect of pH and enzyme concentration on the rate as well as the variation of rate with time. They also showed that pyridoxal-5-phosphate (codecarboxylase) could increa...