Effects of mono-methylindoles on catalytic activity of CYP1A1 in human liver microsomes. Inhibition of CYP1A1 activity by MMI in HLM was assessed using specific enzyme substrate Luciferin-CEE. Two independent experiments were performed, with measurements in duplicates. Panel A: MMI were used in concentrations 0.1 μM, 1 μM, 5 μM, 25 μM, 100 μM and 200 μM. Inhibition of enzyme activity was expressed as the mean ± SD and bar graph shows per cents of remaining activity relative to the control (100%, without MMI). Panel B: Single point inactivation assay, using 200 μM concentration of MMI. Bar graph shows the percentage of inhibition, expressing time-dependent inhibition (TDI) (for details see Materials and Methods).