Romanello Larissa, Serrão Vitor Hugo Balasco, Torini Juliana Roberta, Bird Louise E, Nettleship Joanne E, Rada Heather, Reddivari Yamini, Owens Ray J, DeMarco Ricardo, Brandão-Neto José, Pereira Humberto D'Muniz
Laboratório de Biologia Estrutural, Instituto de Física de São Carlos, Universidade de São Paulo, 13563-120, São Carlos, SP, Brazil.
OPPF-UK, Research Complex at Harwell, Rutherford Appleton Laboratory, Oxford, OX11 0FA, United Kingdom; Division of Structural Biology, University of Oxford, Wellcome Trust Centre for Human Genetics,Roosevelt Drive, Headington, Oxon, OX2 7BN, United Kingdom.
Mol Biochem Parasitol. 2017 Jun;214:27-35. doi: 10.1016/j.molbiopara.2017.03.006. Epub 2017 Mar 25.
Schistosoma mansoni is the parasite responsible for schistosomiasis, a disease that affects about 218 million people worldwide. Currently, both direct treatment and disease control initiatives rely on chemotherapy using a single drug, praziquantel. Concerns over the possibility of resistance developing to praziquantel, have stimulated efforts to develop new drugs for the treatment of schistosomiasis. Schistosomes do not have the de novo purine biosynthetic pathway, and instead depend entirely on the purine salvage pathway to supply its need for purines. The purine salvage pathway has been reported as a potential target for developing new drugs against schistosomiasis. Adenylosuccinate lyase (SmADSL) is an enzyme in this pathway, which cleaves adenylosuccinate (ADS) into adenosine 5'-monophosphate (AMP) and fumarate. SmADSL kinetic characterization was performed by isothermal titration calorimetry (ITC) using both ADS and SAICAR as substrates. Structures of SmADSL in Apo form and in complex with AMP were elucidated by x-ray crystallography revealing a highly conserved tetrameric structure required for their function since the active sites are formed from residues of three different subunits. The active sites are also highly conserved between species and it is difficult to identify a potent species-specific inhibitor for the development of new therapeutic agents. In contrast, several mutagenesis studies have demonstrated the importance of dimeric interface residues in the stability of the quaternary structure of the enzyme. The lower conservation of these residues between SmADSL and human ADSL could be used to lead the development of anti-schistosomiasis drugs based on disruption of subunit interfaces. These structures and kinetics data add another layer of information to Schistosoma mansoni purine salvage pathway.
曼氏血吸虫是导致血吸虫病的寄生虫，这种疾病在全球约影响2.18亿人。目前，直接治疗和疾病控制举措都依赖使用单一药物吡喹酮进行化疗。对吡喹酮产生耐药性可能性的担忧，促使人们努力研发治疗血吸虫病的新药。血吸虫没有从头嘌呤生物合成途径，而是完全依赖嘌呤补救途径来满足其对嘌呤的需求。嘌呤补救途径已被报道为开发抗血吸虫病新药的潜在靶点。腺苷酸琥珀酸裂解酶（SmADSL）是该途径中的一种酶，它将腺苷酸琥珀酸（ADS）裂解为5'-单磷酸腺苷（AMP）和富马酸。使用ADS和SAICAR作为底物，通过等温滴定量热法（ITC）对SmADSL进行了动力学表征。通过X射线晶体学阐明了Apo形式以及与AMP结合的SmADSL的结构，揭示了其功能所需的高度保守的四聚体结构，因为活性位点由三个不同亚基的残基形成。活性位点在不同物种之间也高度保守，难以鉴定出用于开发新治疗剂的有效物种特异性抑制剂。相比之下，多项诱变研究表明二聚体界面残基对该酶四级结构稳定性的重要性。SmADSL与人ADSL之间这些残基的保守性较低，可用于指导基于破坏亚基界面的抗血吸虫病药物的开发。这些结构和动力学数据为曼氏血吸虫嘌呤补救途径增添了另一层信息。
