Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
PLoS One. 2013 Jun 7;8(6):e63764. doi: 10.1371/journal.pone.0063764. Print 2013.
Melanins are synthesized by organisms of all biological kingdoms and comprise a heterogeneous class of natural pigments. Certain of these polymers have been implicated in the pathogenesis of several important human fungal pathogens. This study investigated whether the fungal skin pathogen Malassezia furfur produces melanin or melanin-like compounds. A melanin-binding monoclonal antibody (MAb) labelled in vitro cultivated yeast cells of M. furfur. In addition, melanization of Malassezia yeasts and hyphae was detected by anti-melanin MAb in scrapings from patients with pityriasis versicolor. Treatment of Malassezia yeasts with proteolytic enzymes, denaturant and concentrated hot acid yielded dark particles and electron spin resonance spectroscopy revealed that these particles contained a stable free radical compound, consistent with their identification as melanins. Malassezia yeasts required phenolic compounds, such as L-DOPA, in order to synthesize melanin. L-DOPA also triggered hyphal formation in vitro when combined with kojic acid, a tyrosinase inhibitor, in a dose-dependent manner. In this respect, L-DOPA is thought to be an essential substance that is linked to both melanization and yeast-mycelial transformation in M. furfur. In summary, M. furfur can produce melanin or melanin-like compounds in vitro and in vivo, and the DOPA melanin pathway is involved in cell wall melanization.
黑色素是所有生物王国的生物体合成的，包含一类异构的天然色素。这些聚合物中的某些已被牵连到几种重要的人类真菌病原体的发病机制中。本研究调查了皮肤病原体糠秕马拉色菌是否产生黑色素或类似黑色素的化合物。一种黑色素结合的单克隆抗体（MAb）在体外培养的糠秕马拉色菌酵母细胞上进行了标记。此外，在花斑癣患者的刮屑中，抗黑色素 MAb 检测到了马拉色菌酵母和菌丝的黑色素化。用蛋白酶、变性剂和浓热酸处理马拉色菌酵母，会产生黑色颗粒，电子自旋共振光谱显示这些颗粒含有一种稳定的自由基化合物，与它们被鉴定为黑色素一致。马拉色菌酵母需要酚类化合物，如 L-DOPA，才能合成黑色素。L-DOPA 还与曲酸（一种酪氨酸酶抑制剂）结合，以剂量依赖的方式在体外触发菌丝形成。在这方面，L-DOPA 被认为是一种必需物质，与糠秕马拉色菌中的黑色素化和酵母-菌丝转化都有关。总之，糠秕马拉色菌可以在体外和体内产生黑色素或类似黑色素的化合物，并且 DOPA 黑色素途径参与细胞壁黑色素化。
