Fig. 4.

Human DOPA decarboxylase inhibitor, carbidopa, does not inhibit bacterial tyrosine decarboxylases. a Inhibitory constants (Ki) of bacterial decarboxylases (black) and human DOPA decarboxylase (gray), with fold-difference between bacterial and human decarboxylase displayed on top of the bars. Quantitative comparison of dopamine (DA) production by E. faecium W54, b and E. faecalis v583, c at stationary phase after 15 min, with representative HPLC-ED curve. Bacterial cultures (n = 3) were incubated with 100 µM levodopa (LD) or a 4:1 mixture (in weight) of levodopa and carbidopa (CD) (100 µM levodopa and 21.7 µM carbidopa). Error bars represent SEM (a) or SD (b, c) and significance was tested using a parametric unpaired T-test