Purification of an endogenous inhibitor of L-Dopa decarboxylase activity from human serum.
An endogenous inhibitor of L-Dopa decarboxylase was identified and purified from human serum. In Triton X-114 partitioning experiments, the inhibitor was recovered in the detergent enriched phase, suggesting a hydrophobic nature. Purification was achieved by means of proteinase K digestion, ammonium sulphate precipitation, phenyl sepharose hydrophobic chromatography and subsequent extraction from a nondenaturing polyacrylamide gel. This purification scheme resulted in the isolation of a single 25 kDa band, bearing L-Dopa decarboxylase inhibitory activity. The purified molecule was found to be resistant to heat and digestion by various proteases. Proteolytic digestion of the purified inhibitor by pronase and aminopeptidase M was achieved only following carboxymethylation. The biological importance of the presence of an L-Dopa decarboxylase activity inhibitor in normal biological fluids remains to be elucidated. The better understanding of the regulation of Ddc enzymatic activity could prove valuable in the clarification of the enzyme's role in a series of pathological conditions, as well as, in physiological regulatory mechanisms.
Vassiliou
Alice-Georgia
AG
Dept of Biochemistry and Molecular Biology, University of Athens, Panepistimiopolis 15701, Athens, Greece.
Vassilacopoulou
Dido
D
Fragoulis
Emmanuel G
EG
D000818:Animals; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000097:blood / Q000302:isolation & purification*; D006801:Humans; D051379:Mice
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D004791:Enzyme Inhibitors; D019286:Endopeptidase K