Purification and properties of two malate dehydrogenases from Candida sp. N-16 grown on methanol

Thiamine antivitamins--an opportunity of therapy of fungal infections caused by Malassezia pachydermatis and Candida albicans

Severe skin diseases and systemic fungaemia are caused by Malassezia pachydermatis and Candida albicans respectively. Antifungal therapies are less effective because of chronic character of infections and high percentage of relapses. Therefore, there is a great need to develop new strategies of antifungal therapies. We previously found that oxythiamine decreases proliferation of yeast (Saccharomyces cerevisiae), therefore we suggest that thiamine antivitamins can be considered as antifungal agents. The aim of this study was the comparison of thiamine antivitamins (oxythiamine, amprolium, thiochrome, tetrahydrothiamine and tetrahydrooxythiamine) inhibitory effect on the growth rate and energetic metabolism efficiency in non-pathogenic S. cerevisiae and two potentially pathogenic species M. pachydermatis and C. albicans. Investigated species were cultured on a Sabouraud medium supplemented with trace elements in the presence (40 mg l(-1)) or absence of each tested antivitamins to estimate their influence on growth rate, enzyme activity and kinetic parameters of pyruvate decarboxylase and malate dehydrogenase of each tested species. Oxythiamine was the only antivitamin with antifungal potential. M. pachydermatis and S. cerevisiae were the most sensitive, whereas C. albicans was the least sensitive to oxythiamine action. Oxythiamine can be considered as supportive agent in superficial mycoses treatment, especially those caused by species from the genus Malassezia.

Comparative study of the activity and kinetic properties of malate dehydrogenase and pyruvate decarboxylase from Candida albicans, Malassezia pachydermatis, and Saccharomyces cerevisiae

Candida albicans and Malassezia pachydermatis cause human and animal infections of the skin and internal organs. We compare the properties of two enzymes, pyruvate decarboxylase (PDC) and malate dehydrogenase (MDH), from these species and from Saccharomyces cerevisiae cultivated under aerobic and anaerobic conditions to find differences between the enzymes that adapt pathogens for virulence and help us in searching for new antifungal agents. Malassezia pachydermatis did not show any growth under anaerobic conditions, as opposed to C. albicans and S. cerevisiae. Under aerobic conditions, C. albicans showed the highest growth rate. Malassezia pachydermatis, contrary to the others, did not show any PDC activity, simultaneously showing the highest MDH activity under aerobic conditions and a Km value for oxaloacetate lower than S. cerevisiae. Candida albicans and S. cerevisiae showed a strong decrease in MDH activity under anaerobic conditions. Candida albicans shows four different isoforms of MDH, while M. pachydermatis and S. cerevisiae are characterized by two and three isoforms. Candida albicans shows about a twofold lower activity of PDC but, simultaneously, almost a threefold lower Km value for pyruvate in comparison with S. cerevisiae. The PDC apoform share under aerobic conditions in C. albicans was 47%, while in S. cerevisiae was only 26%; under anaerobic conditions, the PDC apoform decreased to 12% and 8%, respectively. The properties of enzymes from C. albicans show its high metabolic flexibility (contrary to M. pachydermatis) and cause easy switching between fermentative and oxidative metabolism. This feature allows C. albicans to cause both surface and deep infections. We take into consideration the use of thiamin antimetabolites as antifungal factors that can affect both oxidative and fermentative metabolism.