Abstract 16889: A Novel Single-Chain Enzyme Complex With Triple-Catalytic Activities Controlling the Metabolism of Arachidonic Acid Toward the Anti-Bleeding Thromboxane A 2 Biosynthesis

Abstract

Background: One of the most common bleeding emergencies in interventional cardiology and surgical procedures is caused by the use of nonsteroidal anti-inflammatory drugs (NSAIDs), which strongly inhibit enzymatic biosynthesis of thromboxane A 2 (TXA 2 ). Objectives: We want to investigate an effective approach to overcome such NSAIDs-mediated severe bleeding emergencies. Methods: In this study, according to structure-based enzymatic design, we have created a novel single-chain hybrid enzyme complex (SCHEC), COX-1-10-aa-TXAS, by linking the C-terminus of cyclooxygenase-1 (COX-1) to the N-terminus of the TXA 2 synthase (TXAS) through a 10-residue amino acid linker. Results and conclusions: The recombinant COX-1-10aa-TXAS could not only maintain full activities of the parent enzymes, but also more effectively pass COX-1-derived intermediate prostaglandin (PG) H 2 to the active site of TXAS. This results in rapidly redirecting the cellular metabolism of arachidonic acid (AA) toward TXA 2 ; meanwhile, reducing PGH 2 being passed to other prostanoid synthases, such as prostaglandin-I and prostaglandin-E synthases (PGIS, PGES), which compete with TXAS to isomerize PGH 2 into bleeding mediators, prostacyclin (PGI 2 ) and prostaglandin E 2 (PGE 2 ). With these multiple effects, the novel COX-1-10aa-TXAS demonstrated a strong anti-bleeding ability to treat normal bleeding, aspirin-resulted TXA 2 -deficient bleeding, as well as PGI 2 -mediated bleeding in vitro and in vivo . Therefore, this novel SCHEC has a great potential to be developed into a biological anti-bleeding reagent to deal with acute and severe bleeding situations.