Catterall M D, Ward M E, Jacobs P
J Invest Dermatol. 1978 Dec;71(6):398-401. doi: 10.1111/1523-1747.ep12557535.
Pityrosporum orbiculare is an obligate lipophilic yeast in vitro, which suggests it possesses an extracellular lipase crucial for nutrition. If present in vivo, the enzyme would enable the yeast to utilize skin surface lipids, which may therfore play an important role in the pathogenesis of pityriasis versicolor. Cultured P. orbiculare and biopsy material from patients with pityriasis versicolor were investigated for the presence of lipase by electron microscope histochemistry. At sites of lipase activity, fatty acid hydrolyzed from Tween 80 substrate reacts with Ca++ ions to form an insoluble Ca++ soap. Exchange of Ca++ with Pb++ enables the sites of lipase activity to be visualized as electron dense deposits of insoluble lead soap. Surface lipase activity was apparent when the technique was applied to P. orbiculare grown on lipid containing medium and its specificity confirmed by removal of substrate and inhibition by di-isopropyl fluorophosphate and quinine hydrochloride, but not by sodium fluoride. When the same technique was applied to stratum corneum infected with Pityrosporum furfur (Malassez), no reaction product could be detected. It is postulated that lipase, although critical for fungal nutrition in vitro, is unlikely to be of importance in vivo. Skin surface lipids are therefore probably not relevant to the pathogenesis of pityriasis versicolor.
圆形糠秕孢子菌在体外是一种专性嗜脂酵母，这表明它拥有一种对营养至关重要的细胞外脂肪酶。如果在体内存在，该酶将使酵母能够利用皮肤表面脂质，因此这可能在花斑癣的发病机制中起重要作用。通过电子显微镜组织化学研究培养的圆形糠秕孢子菌和花斑癣患者的活检材料中脂肪酶的存在情况。在脂肪酶活性部位，从吐温80底物水解的脂肪酸与钙离子反应形成不溶性钙皂。钙离子与铅离子的交换使脂肪酶活性部位可视化为不溶性铅皂的电子致密沉积物。当该技术应用于在含脂质培养基上生长的圆形糠秕孢子菌时，表面脂肪酶活性明显，通过去除底物以及用二异丙基氟磷酸和盐酸奎宁抑制（但不是用氟化钠抑制）来证实其特异性。当将相同技术应用于被糠秕马拉色菌感染的角质层时，未检测到反应产物。据推测，脂肪酶虽然在体外对真菌营养至关重要，但在体内不太可能起重要作用。因此，皮肤表面脂质可能与花斑癣的发病机制无关。
