Fungal melanin biosynthesis pathway (DHN/DOPA pathway)

The fungal melanin biosynthesis pathway is a critical metabolic route responsible for the production of melanin, a high-molecular-weight pigment essential for fungal survival and pathogenicity [Henson et al., 1999]. In most filamentous fungi, melanin is synthesized via the 1,8-dihydroxynaphthalene (DHN) pathway, while certain yeasts like Cryptococcus neoformans utilize the L-3,4-dihydroxyphenylalanine (DOPA) pathway [Langfelder et al., 2003]. Melanin functions as a biological shield, protecting the fungus from environmental insults such as ultraviolet (UV) radiation, extreme temperatures, and oxidative stress [Nosanchuk & Casadevall, 2003]. Within a host, melanin acts as a potent virulence factor by neutralizing reactive oxygen species produced by immune cells and masking fungal components to evade detection [Upadhyay et al., 2023]. Pharmacological inhibition of this pathway, primarily through melanin biosynthesis inhibitors (MBIs) like tricyclazole, disrupts the formation of the protective pigment, thereby reducing the fungus's ability to infect hosts and survive environmental stress [Henson et al., 1999]. While currently most prevalent in agricultural applications to combat rice blast, this pathway represents a promising target for developing novel clinical antifungals that attenuate virulence rather than directly killing the organism.

Other names

DHN-melanin pathwayDOPA-melanin pathwayFungal melanogenesisPolyketide-derived melanin pathway

Inhibition of specific enzymes within the melanin biosynthetic route, such as 1,3,8-trihydroxynaphthalene reductase (3HNR) or scytalone dehydratase (SDH), which prevents the polymerization of 1,8-dihydroxynaphthalene into melanin [Henson et al., 1999; Upadhyay et al., 2023].