Laccase and melanization in clinically important Cryptococcus species other than Cryptococcus neoformans

Area of Science:

• Mycology
• Biochemistry
• Medical Microbiology

Background:

• Laccase enzyme and melanin synthesis are virulence factors in Cryptococcus neoformans.
• Increasing clinical isolation of non-neoformans Cryptococcus species necessitates investigation into their virulence mechanisms.

Purpose of the Study:

• To investigate the presence and activity of laccase in clinically relevant, non-neoformans Cryptococcus species.
• To determine if these species can synthesize melanin.

Main Methods:

• Enzyme assays using epinephrine substrate to detect laccase activity.
• Cell disruption and fractionation to isolate soluble enzyme components.
• Nondenaturing polyacrylamide gel electrophoresis (PAGE) with activity staining to analyze enzyme migration.
• Melanin band visualization.

Main Results:

• Laccase activity was detected in Cryptococcus albidus, Cryptococcus laurentii, and Cryptococcus curvatus, but not in Cryptococcus humicola.
• Melanin synthesis (adrenochrome color) was observed in C. albidus, C. laurentii, and C. curvatus.
• Enzyme activity levels were lower than in C. neoformans.
• PAGE analysis showed slower migration of laccases from these species compared to C. neoformans.

Conclusions:

• Clinically emerging Cryptococcus species express laccase enzyme activity.
• These species are capable of melanin synthesis, a potential virulence factor.
• Further research into the role of laccase and melanin in the pathogenesis of these emerging fungal pathogens is warranted.