Department of Dermatology and Venereology, First Affiliated Hospital, Guangxi Medical University, Nanning, China.
PLoS One. 2014 Mar 19;9(3):e92610. doi: 10.1371/journal.pone.0092610. eCollection 2014.
The fungal pathogen Penicillium marneffei produces melanin-like pigment in vitro. The synthetic pathway of melanin and its possible influence in the protective yeast cells surviving within macrophage cells are not known. In this work, P. marneffei produced brown black pigment in the presence of L-DOPA and black particles were extracted from yeast cells treated with proteolytic enzymes, denaturant and concentrated hot acid. Kojic acid inhibited the brown-black pigment production of P. marneffei yeast grown on brain heart infusion agar. Transmitting electron microscopy showed spherical granular electron-dense particles with an average diameter of 100 nm in a beaded arrangement in the innermost cell wall. Electron-paramagnetic resonance revealed that the black particles contain a stable free radical compound. The UV-visible and Fourier transform infrared spectra of particles extracted from P. marneffei and synthetic DOPA-melanin showed a high degree of similarity. Melanized yeast cells decreased phagocytosis by macrophage cells and increased resistance to intracellular digestion in vitro. These results indicate that P. marneffei can synthesize DOPA-melanin or melanin-like compounds in vitro and suggest that the DOPA-melanin pathway is associated with cell wall structure and enhances the resistance to phagocytosis by macrophages.
马内菲青霉在体外产生类似于黑色素的色素。黑色素的合成途径及其在保护酵母细胞免受巨噬细胞内吞噬的可能影响尚不清楚。在这项工作中，当 L-DOPA 存在时，P. marneffei 产生棕黑色色素，并且从用蛋白酶、变性剂和浓缩热酸处理的酵母细胞中提取黑色颗粒。曲酸抑制在脑心浸液琼脂上生长的 P. marneffei 酵母的棕黑色色素产生。透射电子显微镜显示，在最内层细胞壁中，以珠状排列的球形颗粒状电子致密颗粒，平均直径为 100nm。电子顺磁共振显示黑色颗粒含有稳定的自由基化合物。从 P. marneffei 和合成 DOPA-黑色素提取的颗粒的紫外-可见和傅立叶变换红外光谱显示出高度的相似性。黑色素化酵母细胞降低了巨噬细胞的吞噬作用，并增加了体外对细胞内消化的抵抗力。这些结果表明，P. marneffei 可以在体外合成 DOPA-黑色素或类似黑色素的化合物，并表明 DOPA-黑色素途径与细胞壁结构有关，并增强了对巨噬细胞吞噬作用的抵抗力。
