Toviwek Borvornwat, Koonawootrittriron Skorn, Suwanasopee Thanathip, Jattawa Danai, Pongprayoon Prapasiri
Department of Chemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900, Thailand.
Department of Animal Science, Faculty of Agriculture, Kasetsart University, Chatuchak, Bangkok 10900, Thailand.
J Phys Chem B. 2024 Dec 5;128(48):11876-11884. doi: 10.1021/acs.jpcb.4c05571. Epub 2024 Nov 22.
Human carnosinases (CNs) are Xaa-His metal-ion-activated aminopeptidases that break down bioactive carnosine and other histidine-containing dipeptides. Carnosine is a bioactive peptide found in meat and prevalently used as a supplement and in functional food formulation. Nonetheless, carnosine is digested by CNs rapidly after ingestion. CNs have two isoforms (carnosinase 1 (CN1) and carnosinase 2 (CN2)), where CN1 is the main player in carnosine digestion. CNs contain a catalytic metal ion pair (Zn for CN1 and Mn for CN2) and two subpockets (S1 and S1' pockets) to accommodate a substrate. Bestatin (BES) has been reported to be active for CN2; however, its inhibition ability for CN1 has remained under debate, because the underlying mechanism remains unclear. This information is important for designing novel CN1-selective inhibitors for proliferating carnosine after ingestion. Thus, molecular dynamics (MD) simulations were performed to explore the binding mechanism of BES to both CN1 and CN2. The binding of BES-CN1 and BES-CN2 was studied in comparison. The results indicated that BES could bind both CNs with different degrees of binding affinity. BES prefers CN2 because: (1) its aryl terminus is trapped by Y197 in an S1 pocket; (ii) the BES polar backbone is firmly bound by catalytic Mn ions; and (iii) the S1' pocket can shrink to accommodate the isopropyl end of BES. In contrast, the high mobility of the aryl end and the complete loss of metal-BES interactions in CN1 cause a loose BES binding. Seemingly, polar termini were required for a good CN1 inhibitor.
人肌肽酶（CNs）是Xaa-His金属离子激活的氨肽酶，可分解生物活性肌肽和其他含组氨酸的二肽。肌肽是一种存在于肉类中的生物活性肽，广泛用作补充剂和功能性食品配方。尽管如此，肌肽在摄入后会迅速被CNs消化。CNs有两种同工型（肌肽酶1（CN1）和肌肽酶2（CN2）），其中CN1是肌肽消化的主要参与者。CNs包含一个催化金属离子对（CN1为锌，CN2为锰）和两个亚口袋（S1和S1'口袋）以容纳底物。据报道，贝司他汀（BES）对CN2有活性；然而，其对CN1的抑制能力仍存在争议，因为潜在机制尚不清楚。这些信息对于设计新型CN1选择性抑制剂以在摄入后增加肌肽含量很重要。因此，进行了分子动力学（MD）模拟以探索BES与CN1和CN2的结合机制。比较研究了BES-CN1和BES-CN2的结合。结果表明，BES可以以不同程度的结合亲和力与两种CNs结合。BES更倾向于CN2，原因如下：（1）其芳基末端被Y197捕获在S1口袋中；（ii）BES极性主链被催化锰离子牢固结合；（iii）S1'口袋可以收缩以容纳BES的异丙基末端。相比之下，芳基末端的高迁移率以及CN1中金属-BES相互作用的完全丧失导致BES结合松散。显然，极性末端是良好的CN1抑制剂所必需的。
