Detection, Purification and Identification of An Endogenous Inhibitor of l-Dopa Decarboxylase Activity from Human Placenta

Abstract

An endogenous inhibitor of L-Dopa decarboxylase activity was identified and purified from human placenta. The endogenous inhibitor of L-Dopa decarboxylase (Ddc) was localized in the membrane fraction of placental tissue. Treatment of membranes with phosphatidylinositol-specific phospholipase C or proteinase K did not affect membrane-associated Ddc inhibitory activity, suggesting that a population of the inhibitor is embedded within membranes. Purification was achieved by extraction from a nondenaturing polyacrylamide gel. The purification scheme resulted in the isolation of a single 35 kDa band, bearing L-Dopa decarboxylase inhibitory activity. The purified inhibitor was identified as Annexin V. The elucidation of the biological importance of the presence of an L-Dopa decarboxylase activity inhibitor in normal human tissues could provide us with new information leading to the better understanding of the biological pathways that Ddc is involved in.

DDC (dopa decarboxylase (aromatic L-amino acid decarboxylase))

“…2010; 14(10) the full-length DDC protein sequence (Vassilacopoulou et al, 2004). Although previous data had suggested that DDC was a rather unregulated molecule, several findings have indicated that DDC activity can be modulated by many factors, such as D1, DA receptor antagonists (Rossetti et al, 1990), a 2 -adrenergic receptor antagonists (Rossetti et al, 1989), D1, D2 receptor antagonists (Zhu et al, 1992;Hadjiconstantinou et al, 1993), DA receptor agonists (Zhu et al, 1993), PK-A and PK-C mediated pathways (Young et al, 1993;Young et al, 1994) and by endogenous inhibitors isolated from human serum (Vassiliou et al, 2005) and placenta (Vassiliou et al, 2009).…”

Release of Membrane-Associated L-Dopa Decarboxylase from Human Cells

“…DDC has been purified from a variety of sources [20,29,38,41,49,59]. Although DDC was thought to be a rather unregulated enzyme, several lines of evidence have shown that DDC activity can be modulated by a multitude of factors, such as Dopamine receptor agonists and antagonists [25,47,62,63], a 2 -adrenergic receptor antagonists [46], PK-A and PK-C mediated pathways [60,61] and endogenous inhibitors [57,58].…”

Human l-DOPA decarboxylase mRNA is a target of miR-145: A prediction to validation workflow

“…Similar to data emerged from studies in insects (Poulikakos et al, 2002) and rodents (Poulikakos et al, 2001) human DDC can be either targeted in the membranes or found in the cytosol of the cells (Chalatsa et al, 2011). In parallel, its enzymatic activity has proven to be affected by various factors, including specific inhibitors (Vassiliou et al, 2009). Likewise, the expression of DDC can be widely regulated in human cells.…”