Ramírez-Montiel Fátima Berenice, Andrade-Guillen Sairy Yarely, Medina-Nieto Ana Laura, Rangel-Serrano Ángeles, Martínez-Álvarez José A, de la Mora Javier, Vargas-Maya Naurú Idalia, Mendoza-Macías Claudia Leticia, Padilla-Vaca Felipe, Franco Bernardo
Departamento de Farmacia, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, Guanajuato 36050, Mexico.
Departamento de Biología, División de Ciencias Naturales y Exactas, Universidad de Guanajuato, Noria Alta s/n, Guanajuato 36050, Mexico.
Pathogens. 2025 Jan 5;14(1):32. doi: 10.3390/pathogens14010032.
The path to survival for pathogenic organisms is not straightforward. Pathogens require a set of enzymes for tissue damage generation and to obtain nourishment, as well as a toolbox full of alternatives to bypass host defense mechanisms. Our group has shown that the parasitic protist encodes for 14 sphingomyelinases (SMases); one of them (acid sphingomyelinase 6, aSMase6) is involved in repairing membrane damage and exhibits hemolytic activity. The enzymatic characterization of aSMase6 has been shown to be activated by magnesium ions but not by zinc, as shown for the human aSMase, and is strongly inhibited by cobalt. However, no structural data are available for the aSMase6 enzyme. In this work, bioinformatic analyses showed that the protist aSMases are diverse enzymes, are evolutionarily related to hemolysins derived from bacteria, and showed a similar overall structure as parasitic, free-living protists and mammalian enzymes. AlphaFold3 models predicted the occupancy of cobalt ions in the active site of the aSMase6 enzyme. Cavity blind docking showed that the substrate is pushed outward of the active site when cobalt is bound instead of magnesium ions. Additionally, the structural models of the aSMase6 of showed a loop that is absent from the rest of the aSMases, suggesting that it may be involved in hemolytic activity, as demonstrated experimentally using the recombinant proteins of aSMase4 and aSMase6. enzymes show a putative transmembrane domain and seem functionally different from . This work provides insight into the future biochemical analyses that can show mechanistic features of parasitic protists sphingomyelinases, ultimately rendering these enzymes potential therapeutic targets.
致病生物的生存之路并非一帆风顺。病原体需要一系列酶来造成组织损伤并获取营养，还需要一整套替代方法来绕过宿主防御机制。我们的研究小组发现，这种寄生原生生物编码了14种鞘磷脂酶（SMases）；其中一种（酸性鞘磷脂酶6，aSMase6）参与修复膜损伤并具有溶血活性。已证明aSMase6的酶学特性如人类aSMase一样可被镁离子激活但不能被锌激活，并且强烈受钴抑制。然而，尚无aSMase6酶的结构数据。在这项工作中，生物信息学分析表明，原生生物的aSMases是多样的酶，在进化上与源自细菌的溶血素相关，并且与寄生、自由生活的原生生物和哺乳动物的酶具有相似的整体结构。AlphaFold3模型预测了钴离子在aSMase6酶活性位点的占据情况。空穴盲对接表明，当结合钴离子而非镁离子时，底物被推离活性位点。此外，aSMase6的结构模型显示出一个在其他aSMases中不存在的环，这表明它可能参与溶血活性，这一点已通过使用aSMase4和aSMase6的重组蛋白进行实验证明。 酶显示出一个推定的跨膜结构域，并且在功能上似乎与 不同。这项工作为未来的生化分析提供了见解，这些分析可以揭示寄生原生生物鞘磷脂酶的机制特征，最终使这些酶成为潜在的治疗靶点。
