Sulyman Abdulhakeem O, Fulcher Jessie, Crossley Samuel, Fatokun Amos A, Olorunniji Femi J
Department of Biochemistry, Faculty of Pure and Applied Sciences, Kwara State University, Malete 241103, Nigeria.
School of Pharmacy & Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK.
BioTech (Basel). 2023 Sep 20;12(3):59. doi: 10.3390/biotech12030059.
Low-molecular-weight protein tyrosine phosphatases (LMW-PTPs) are involved in promoting the intracellular survival of (Mtb), the causative organism of tuberculosis. These PTPs directly alter host signalling pathways to evade the hostile environment of macrophages and avoid host clearance. Among these, protein tyrosine phosphatase A (Mt-PTPa) is implicated in phagosome acidification failure, thereby inhibiting phagosome maturation to promote () survival. In this study, we explored Mt-PTPa as a potential drug target for treating . We started by screening a library of 502 pure natural compounds against the activities of Mt-PTPa in vitro, with a threshold of 50% inhibition of activity via a <500 µM concentration of the candidate drugs. The initial screen identified epigallocatechin, myricetin, rosmarinic acid, and shikonin as hits. Among these, the naphthoquinone, shikonin (5, 8-dihydroxy-2-[(1R)-1-hydroxy-4-methyl-3-pentenyl]-1,4-naphthoquinone), showed the strongest inhibition (IC 33 µM). Further tests showed that juglone (5-hydroxy-1,4-naphthalenedione), another naphthoquinone, displayed similar potent inhibition of Mt-PTPa to shikonin. Kinetic analysis of the inhibition patterns suggests a non-competitive inhibition mechanism for both compounds, with inhibitor constants (Ki) of 8.5 µM and 12.5 µM for shikonin and juglone, respectively. Our findings are consistent with earlier studies suggesting that Mt-PTPa is susceptible to specific allosteric modulation via a non-competitive or mixed inhibition mechanism.
低分子量蛋白酪氨酸磷酸酶（LMW-PTPs）参与促进结核分枝杆菌（Mtb，结核病的病原体）在细胞内的存活。这些磷酸酶直接改变宿主信号通路，以逃避巨噬细胞的恶劣环境并避免被宿主清除。其中，蛋白酪氨酸磷酸酶A（Mt-PTPa）与吞噬体酸化失败有关，从而抑制吞噬体成熟以促进结核分枝杆菌（Mtb）的存活。在本研究中，我们探索了将Mt-PTPa作为治疗结核病的潜在药物靶点。我们首先针对Mt-PTPa的体外活性筛选了一个包含502种纯天然化合物的文库，候选药物浓度<500 µM时活性抑制阈值为50%。初步筛选确定表没食子儿茶素、杨梅素、迷迭香酸和紫草素为阳性结果。其中，萘醌类化合物紫草素（5,8-二羟基-2-[(1R)-1-羟基-4-甲基-3-戊烯基]-1,4-萘醌）显示出最强的抑制作用（IC 33 µM）。进一步测试表明，另一种萘醌类化合物胡桃醌（5-羟基-1,4-萘二酮）对Mt-PTPa的抑制作用与紫草素相似。对抑制模式的动力学分析表明，这两种化合物均为非竞争性抑制机制，紫草素和胡桃醌的抑制常数（Ki）分别为8.5 µM和12.5 µM。我们的研究结果与早期研究一致，表明Mt-PTPa易受通过非竞争性或混合抑制机制进行的特异性变构调节。
