Involved in the biosynthesis of melanin but also various secondary metabolites containing a naphthoquinone ring. Catalyzes the iterative condensation of five CoA-linked malonyl units to form a pentaketide intermediate. THNS subsequently catalyzes the dual intramolecular Claisen and aldol condensations of this linear intermediate to produce the fused ring of 1,3,6,8-tetrahydroxynaphthalene (THN). 5 H(+) + 5 malonyl-CoA = 5 CO2 + 5 CoA + H2O + naphthalene-1,3,6,8-tetrol Pigment biosynthesis; melanin biosynthesis. Homodimer. Cells lacking this gene are unable to produce melanin in hyphae, resulting in albino mycelium, however there is no effect on growth or morphological development. Belongs to the thiolase-like superfamily. Chalcone/stilbene synthases family.