Engineered Substrate for Cyclooxygenase-2: A Pentapeptide Isoconformational to Arachidonic Acid for Managing Inflammation

Beyond the conventional mode of working
of anti-inflammatory agents through enzyme inhibition, herein, COX-2
was provided with an alternate substrate. A proline-centered pentapeptide
isoconformational to arachidonic acid, which exhibited appreciable
selectivity for COX-2, overcoming acetic acid- and formalin-induced
pain in rats to almost 80%, was treated as a substrate by the enzyme.
Remarkably, COX-2 metabolized the pentapeptide into small fragments
consisting mainly of di- and tripeptides that ensured the safe breakdown
of the peptide under in vivo conditions. The kinetic parameter Kcat/Km for COX-2-mediated
metabolism of the peptide (6.3 × 105 M–1 s–1) was quite similar to 9.5 × 105 M–1 s–1 for arachidonic acid.
Evidenced by the molecular dynamic studies and the use of Y385F COX-2,
it was observed that the breakage of the pentapeptide has probably
been taken place through H-bond activation of the peptide bond by
the side chains of Y385 and S530.

不同于抗炎剂通过酶抑制作用发挥功效的传统范式，本研究为环氧合酶-2（COX-2）提供了一种替代底物。一种以脯氨酸为中心、与花生四烯酸构象同源的五肽，对环氧合酶-2展现出显著的选择性，可使大鼠的乙酸及福尔马林诱导性疼痛抑制率接近80%，且可被该酶识别为底物。值得注意的是，环氧合酶-2可将该五肽代谢为主要由二肽和三肽组成的小分子片段，这确保了该肽在体内条件下的安全降解。该五肽经环氧合酶-2介导代谢的动力学参数Kcat/Km为(6.3 × 10^5 M⁻¹·s⁻¹)，与花生四烯酸的(9.5 × 10^5 M⁻¹·s⁻¹)极为相近。通过分子动力学研究以及使用Y385F COX-2的实验佐证，研究人员观察到该五肽的断裂可能是通过Y385与S530的侧链对肽键的氢键活化作用实现的。