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Browsing by Subject "tyrosine decarboxylase"

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  • Evaluation of potential dual inhibition of Dopa and Tyrosine Decarboxylases in the L-dopa treatment of Parkinson’s disease 
    Paakkunainen, Jonna (2023)
    Parkinson’s disease is a progressive neurodegenerative disorder which is commonly treated with Levodopa (L-dopa) and Dopa Decarboxylase (DDC)/ Catechol-O-methyltransferase (COMT) inhibitors. The main problem with this treatment is the intestinal conversion of L-dopa to dopamine despite DDC and COMT inhibition which probably occurs by the Tyrosine Decarboxylase (TyrDC) of intestinal bacteria. This study aims to find new inhibitor molecules that would have dual inhibitory effects towards both DDC and TyrDC enzymes. Currently, available DDC inhibitors cannot inhibit the bacterial TyrDC enzyme. A recently found TyrDC inhibitor (S)-α-Fluoromethyltyrosine (AFMT) is not able to inhibit the human DDC enzyme, respectively. The dual inhibition of both decarboxylases could reduce the dosing frequency and side effects related to L-dopa. In addition, the object of this study is to produce the human DDC enzyme by DNA recombinant technique as well as develop and optimize a biochemical DDC inhibition assay to study the effect of selected small molecule compounds towards inhibition of DDC and L-dopa conversion in E. faecalis model by previously developed cell-based assay. The human DDC was successfully produced in a TB medium with a yield of 1.8 mg/mL. The Km value of DDC for L-dopa was found to be 34 μM which indicates a high affinity for L-dopa. In the optimization of the DDC inhibition assay, the sample volume of 80 μL and incubation time of 3 h with detection reagent was found to give the highest fluorometric signal with sufficient robustness. In the initial screening of test compounds, 14 % of the compounds (n=59) were classified as active towards human DDC, while 31 % of the compounds were active towards L-dopa conversion in the E. faecalis model. Of those compounds, five were having dose-dependent dual inhibitory effects, but the IC50 values of them were higher compared to either carbidopa or AFMT. The most effective compounds were 8009-2501 (IC50 37 μM in E. faecalis model and 19 % inhibition at 1000 μM towards DDC enzyme) and 8012-3386 (IC50 248 μM in E. faecalis model and 37 % inhibition at 1000 μM towards DDC enzyme). However, this study confirms the possibility to find dual decarboxylase inhibitors. By optimizing the structures as well as investigating the mechanism of action, selectivity, and structure-activity relationships of the most active compounds, it is possible to find more effective dual inhibitors in the future.
  • Synthesis, purification, and characterization of novel dual inhibitors of tyrosine decarboxylase and dopa decarboxylase 
    Henrik, Häkkinen (2024)
    Parkinson’s disease (PD) is a prevalent neurodegenerative disease characterized by movement disorders, such as bradykinesia, akinesia, and tremor. The degeneration of dopaminergic neurons in the central nervous system (CNS) is the most central aspect of the pathophysiology of PD-related movement disorders. The treatment of PD motor symptoms is based on increasing the diminished dopaminergic signalling in the CNS. This can be achieved by using medications such as dopamine agonists and monoamine oxidase B inhibitors. Levodopa, which acts as a precursor of dopamine in the body, is currently considered the most effective treatment for PD motor symptoms. Unlike dopamine, levodopa can cross the blood-brain barrier. Thus, levodopa must reach the CNS before being metabolized into dopamine to achieve the desired therapeutic effect. Dopa decarboxylase (DDC) inhibitors and catechol-O-methyltransferase inhibitors have been co-administered alongside levodopa to reduce its peripheral metabolism. However, when administered orally, levodopa is also metabolized in the gut by tyrosine decarboxylase, an enzyme produced by gut bacteria. Inhibi tion of bacterial tyrosine decarboxylase (TyrDC) could increase the effectiveness of levodopa treatment and reduce the needed levodopa dosage. The aim of this study was to synthesize and assess the biological activity of novel analogues of previously identified hit compounds which are dual inhibitors of TyrDC and DDC. Our goal was also to gain a deeper understanding of the structure-activity relationships of these compounds. Some of the compounds synthesized in this study were able to inhibit both TyrDC and DDC. Unfortunately, they were also either toxic towar ds human cells, and/or lacked efficacy in a bacterial cell-based assay used to determine the inhibition of levodopa metabolism. However, the data generated in this study can be utilized to design and synthesize new analogs to discover more efficacious and safer TyrDC and DDC dual inhibitors.

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