O-methyltransferase involved in the biosynthesis of methoxylated coumarins natural products such as isoscopoletin, scopoletin, xanthotoxin and bergapten, photosensitizers used for medical purpose such as treating psoriasis and vitiligo or facilitating resistance to microbial infection and other stresses (PubMed:30934718). Catalyzes the methylation of esculetin, bergaptol and xanthotoxol, but seems inactive on scopoletin and isoscopoletin (PubMed:30934718). bergaptol + S-adenosyl-L-methionine = bergapten + S-adenosyl-L-homocysteine S-adenosyl-L-methionine + xanthotoxol = H(+) + S-adenosyl-L-homocysteine + xanthotoxin esculetin + S-adenosyl-L-methionine = H(+) + isoscopoletin + S-adenosyl-L-homocysteine esculetin + S-adenosyl-L-methionine = H(+) + S-adenosyl-L-homocysteine + scopoletin Inhibited by zinc Zn(2+), copper Cu(2+) and silver Ag(+) ions. Optimum pH is 7.5. Aromatic compound metabolism. Secondary metabolite biosynthesis. Homodimer. Expressed ubiquitously. Induced by UV light and hydrogen peroxyde H(2)O(2). Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family. COMT subfamily.