Inactivation of myeloperoxidase by benzoic acid hydrazide

Abstract

Myeloperoxidase (MPO) is expressed by myeloid cells for the purpose of catalyzing the formation of hypochlorous acid, from chloride ions and reaction with a hydrogen peroxide-charged heme covalently bound to the enzyme. Most peroxidase enzymes both plant and mammalian are inhibited by benzoic acid hydrazide (BAH)-containing compounds, but the mechanism underlying MPO inhibition by BAH compounds is largely unknown. Recently, we reported MPO inhibition by BAH and 4-(trifluoromethyl)-BAH was due to hydrolysis of the ester bond between MPO heavy chain glutamate 242 (Glu242) residue and the heme pyrrole A ring, freeing the heme linked light chain MPO subunit from the larger remaining heavy chain portion. Here we probed the structure and function relationship behind this ester bond cleavage using a panel of BAH analogs to gain insight into the constraints imposed by the MPO active site and channel leading to the buried protoporphyrin IX ring. In addition, we show evidence that destruction of the heme ring does not occur by tracking the heme prosthetic group and provide evidence that the mechanism of hydrolysis follows a potential attack of the Glu242 carbonyl leading to a rearrangement causing the release of the vinyl-sulfonium linkage between HC-Met243 and the pyrrole A ring.

Methods for measuring myeloperoxidase activity toward assessing inhibitor efficacy in living systems

“…Other Soret bands are responsible for the green coloration of the MPO protein, namely bands at 496, 570, 620, and 690 nm [40]. Our recent study found that some potent MPO inhibitors, like benzoic acid hydrazide and its analogs, cause disruption of these important ester linkages [41,42]. In mammalian peroxidase, these linkages are thought to impart a level of resistance to the powerful oxidants that they produce, namely HOCl and HOBr, for MPO and LPO, respectively [43].…”

“…3A). Previously, we used stopped flow spectroscopy and the ADHP substrate to study MPO inhibition by benzoic acid hydrazide and its analogs [41,42]. ADHP has also been used in tissue-based assays for determining the presence of MPO activity, as a surrogate for assessing inflammation [63].…”

Pharmacological Therapeutics Targeting RNA-Dependent RNA Polymerase, Proteinase and Spike Protein: From Mechanistic Studies to Clinical Trials for COVID-19

“…Recent studies demonstrate that excessive recruitment of neutrophils and formation of neutrophil extracellular traps results in acute lung injury of influenza pneumonitis [127]. In addition, neutrophil-derived myeloperoxidase (MPO) serves as a potent tissue damage factor and also contributes to influenza pneumonia in mice infected with influenza virus [128][129][130][131]. In addition, coronavirus infection is able to induce stress response, autophagy, apoptosis, and activate innate immunity [40].…”

Roles of Reconstituted High-Density Lipoprotein Nanoparticles in Cardiovascular Disease: A New Paradigm for Drug Discovery

“…MPO plays important roles in the inflammatory response and perpetuation of chronic inflammation in atherosclerosis [75]. Inactivation of MPO reduced reactive oxygen species (ROS)-mediated vascular inflammation and atherosclerosis [97][98][99]. Several imaging agents targeting myeloperoxidase were developed to monitor the inflammatory response and macrophage accumulation [75,[100][101][102].…”