Cryptococcus neoformans laccase catalyses melanin synthesis from both D- and L-DOPA

Area of Science:

• Mycology
• Biochemistry
• Pathogen Biology

Background:

• Cryptococcus neoformans, a human fungal pathogen, synthesizes melanin for protection against environmental and host defenses.
• Melanin production is catalyzed by the enzyme laccase, which oxidizes 3,4-dihydroxyphenylalanine (DOPA) into a pigment within the yeast cell wall.

Purpose of the Study:

• To investigate the stereoselectivity of Cryptococcus neoformans in utilizing different enantiomers of DOPA for melanin synthesis.
• To characterize melanin produced from D-DOPA and compare it with melanin derived from L-DOPA.

Main Methods:

• Culturing Cryptococcus neoformans isolates with L-DOPA and D-DOPA.
• Isolation and biophysical characterization (EPR, zeta potential, antibody binding, electron microscopy) of melanin particles.
• Quantification of DOPA utilization rates.

Main Results:

• Cryptococcus neoformans produced pigments from both L-DOPA and D-DOPA.
• D-DOPA-derived melanin particles exhibited similar properties (free-radical signal, zeta potential, antibody binding, architecture) to L-DOPA-derived particles.
• The utilization rates of L-DOPA and D-DOPA by C. neoformans were comparable.

Conclusions:

• Cryptococcus neoformans demonstrates minimal stereoselectivity in DOPA utilization for melanin synthesis.
• The ability to utilize both L- and D-DOPA broadens the substrate pool for melanization, potentially enhancing fungal survival.
• Understanding DOPA utilization could inform the development of novel therapeutic inhibitors targeting fungal laccase.