Rüchel R, Böning B, Borg M
Infect Immun. 1986 Aug;53(2):411-9. doi: 10.1128/iai.53.2.411-419.1986.
The opportunistic yeastlike fungi of the genus Candida comprise three species which are proteolytic in vitro. Among them, C. albicans and C. tropicalis are of foremost medical importance. However, a strict correlation between extracellular proteolytic activity and virulence is opposed by the low virulence of the third proteolytic species, C. parapsilosis. We purified the secretory acid proteinase of C. parapsilosis (clinical isolate 265). The enzyme is a carboxyl proteinase (EC 3.4.23) like all other secretory Candida proteinases handled so far. Proteinase 265 is distinguished by a lower molecular weight (approximately 33,000); it has increased hydrophobicity, which accounts for inhibition of the enzyme by hemin, and required the presence of nonionic detergent in the initial steps of purification. The enzyme already undergoes alkaline denaturation at neutrality. Its activity is thus confined to the acid microenvironment of the fungal cell wall. Within this range, the enzyme may degrade immunoglobulins like immunoglobulin A1 (IgA1), IgA2, and secretory IgA. No indication was found for glycosylation of proteinase 265 and the related enzyme of C. albicans CBS 2730. However, the comparable proteinase of C. tropicalis 293 was identified as a manno protein. Antiserum against proteinase 265 cross-reacted strongly with corresponding enzymes from other Candida species. Antisera against proteinases of C. albicans and C. tropicalis reacted only weakly with proteinase 265. Thus, secretory Candida proteinases are likely to possess common and species-specific antigenic sites. In contrast to C. albicans, infection of phagocytes by C. parapsilosis 265 was not accompanied by secretion of fungal proteinase. This lack of induction of the enzyme under conditions of infection may account for the low virulence of most isolates of C. parapsilosis.
念珠菌属的机会性酵母样真菌包含三种在体外具有蛋白水解作用的菌种。其中，白色念珠菌和热带念珠菌具有最重要的医学意义。然而，第三种具有蛋白水解作用的菌种近平滑念珠菌的低毒力与细胞外蛋白水解活性和毒力之间的严格相关性相悖。我们纯化了近平滑念珠菌（临床分离株265）的分泌性酸性蛋白酶。该酶是一种羧基蛋白酶（EC 3.4.23），与迄今所研究的所有其他念珠菌分泌性蛋白酶一样。蛋白酶265的特点是分子量较低（约33,000）；其疏水性增加，这导致血红素对该酶具有抑制作用，并且在纯化的初始步骤中需要非离子洗涤剂的存在。该酶在中性条件下就已发生碱性变性。因此，其活性局限于真菌细胞壁的酸性微环境中。在此范围内，该酶可能会降解免疫球蛋白，如免疫球蛋白A1（IgA１）、IgA2和分泌型IgA。未发现蛋白酶265和白色念珠菌CBS 2730的相关酶存在糖基化的迹象。然而，热带念珠菌293的可比蛋白酶被鉴定为一种甘露糖蛋白。抗蛋白酶265的抗血清与其他念珠菌属菌种的相应酶发生强烈交叉反应。抗白色念珠菌和热带念珠菌蛋白酶的抗血清与蛋白酶265的反应较弱。因此，念珠菌分泌性蛋白酶可能具有共同的和种属特异性的抗原位点。与白色念珠菌不同，近平滑念珠菌265感染吞噬细胞时并未伴随真菌蛋白酶的分泌。在感染条件下该酶缺乏诱导作用可能是大多数近平滑念珠菌分离株毒力较低的原因。
