"It is also a selective inhibitor of the human cytochrome P450 isozyme 2D6 (CYP 2D6)"
https://www.ncbi.nlm.nih.gov/pubmed/16149329
"the inhibitions on human liver CYP3A4 and CYP2D6 enzymes by those β-carboline alkaloids were studied kinetically. Harmine, harmol and harmane exhibited noncompetitive inhibition on the activity of CYP3A4 with K(i) values of 16.76, 5.13 and 1.66 μM, respectively. These β-carboline alkaloids were also found to be both substrates and inhibitors for CYP2D6. Harmaline, harmine and harmol showed typical competitive inhibition on the activity of CYP2D6
Inhibition of Human Cytochrome P450 Enzymes 3A4 and 2D6 by β-Carboline Alkaloids, Harmine Derivatives (PDF Download Available). Available from: https://www.researchgate.net/publication/50834428_Inhibition... [accessed Oct 1, 2017]."
https://www.researchgate.net/publication/50834428_Inhibition...