Cryptococcus neoformans laccase catalyses melanin synthesis from both D- and L-DOPA.
The human fungal pathogen Cryptococcus neoformans produces melanin in the presence of various substrates, including the L enantiomer of 3,4-dihydroxyphenylalanine (DOPA). The enzyme laccase catalyses the formation of melanin by oxidizing L-DOPA, initiating a series of presumably spontaneous reactions that ultimately leads to the polymerization of the pigment in the yeast cell wall. There, melanin protects the cell from a multitude of environmental and host assaults. Thus, the ability of C. neoformans to produce pigments from a variety of available substrates is likely to confer a survival advantage. A number of C. neoformans isolates of different serotypes produced pigments from D-DOPA, the stereoisomer of L-DOPA. Acid-resistant particles were isolated from pigmented C. neoformans cells grown in the presence of D-DOPA. Biophysical characterization showed the particles had a stably detectable free-radical signal by EPR, and negative zeta potential, similar to L-DOPA-derived particles. No major differences were found between L- and D-DOPA ghosts in terms of binding to anti-melanin antibodies, or in overall architecture when imaged by electron microscopy. C. neoformans cells utilized L- and D-DOPA at a similar rate. Overall, our results indicate that C. neoformans shows little stereoselectivity for utilizing DOPA in melanin synthesis. The ability of C. neoformans to use both L and D enantiomers for melanization implies that this organism has access to a greater potential pool of substrates for melanin synthesis, and this could potentially be exploited in the design of therapeutic inhibitors of laccase.
Eisenman
Helene C
HC
Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Mues
Mascha
M
Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Weber
Sarah E
SE
Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Frases
Susana
S
Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Chaskes
Stuart
S
Department of Biology, Farmingdale State College, 2350 Broadhollow Road, Farmingdale, NY 11735, USA.
Gerfen
Gary
G
Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Casadevall
Arturo
A
Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
D002473:Cell Wall / Q000378:metabolism; D003455:Cryptococcus neoformans / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D003470:Culture Media; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006801:Humans; D007700:Kinetics; D042845:Laccase / Q000378:metabolism*; D008543:Melanins / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D013237:Stereoisomerism; D013379:Substrate Specificity
D003470:Culture Media; D005609:Free Radicals; D008543:Melanins; D004295:Dihydroxyphenylalanine; D042845:Laccase