Involved in the biosynthesis of acridine alkaloids. N-methyltransferase with a strict substrate specificity for anthranilate. No activity with anthranilic acid methyl ester, anthraniloyl CoA, 3- or 4-amino-benzoic acid, salicylic acid, catechol, eugenol, caffeic acid, quercetin, theobromin, theophyllin, putrescine and nicotinic acid among others. anthranilate + S-adenosyl-L-methionine = H(+) + N-methylanthranilate + S-adenosyl-L-homocysteine Inhibited by Ca(2+), Co(2+), Fe(2+), Fe(3+), Cu(2+) or Zn(2+). No effect of Mg(2+). Optimum pH is 7.5. Optimum temperature is 37 degrees Celsius. Homodimer. Expressed in leaves, flowers, stems and roots. Detected in the vascular tissues in stems, in the rhizodermis or the endodermis of roots, in the inside of carpels, in the central vascular bundles of the syncarp ovary and in the secretory oil glands located around the outer ovary wall. Up-regulated by yeast elicitor treatment. Belongs to the class I-like SAM-binding methyltransferase superfamily. Cation-independent O-methyltransferase family. COMT subfamily.