Structural and mechanistic investigation towards the regulation of M.tb isocitrate lyase
type: CreativeWork
description: Isocitrate lyase (ICL) is a crucial enzyme for the virulence and survival of Mycobacterium tuberculosis (M. tb) during infection. It is a key enzyme of the glyoxylate shunt and the methylcitrate cycle, metabolic pathways that are central to the bacteria’s carbon and lipid metabolism. The absence of ICL in mammals makes it a potential inhibition target for developing new treatments against tuberculosis. In M. tb, ICL exists in two isoforms, ICL1 and ICL2. Although numerous biochemical studies have been conducted to study M. tb ICL since the publication of the first ICL1 structure in 2000, key questions regarding the role of the two M. tb ICL isoforms and their modulation remain unresolved. The work described in this thesis investigates the regulation of ICL from structural and mechanistic perspectives. In particular, it focuses on the inhibition of M. tb ICL by the human macrophage metabolite itaconate, and the activation of M. tb ICL2 by lipid metabolite acetyl-coenzyme A (acetyl-CoA) and its structural analogues. The interactions between host and pathogen are important for M. tb as the bacteria may reside inside its human host for decades. Human macrophages produce itaconate as an antimicrobial metabolite. Previous studies have shown that it may act as an inhibitor of ICL, although its mode of action is not known. In this work, by using protein X-ray crystallography, mass spectrometry and mutagenesis, it was demonstrated that itaconate binds covalently to the active site cysteine of both M. tb ICL1 and ICL2. In addition, it was found that the presence of the ICL reaction product, glyoxylate, may enhance the rate of covalent modification. This work not only provides important structural information about the design of covalent ICL inhibitors, but it also provides insights into the catalytic mechanism of the enzyme, in particular the ‘back reaction’ that converts glyoxylate and succinate to itaconate. Hampered by the lack of structural information, the biological rol…
abstract: Isocitrate lyase (ICL) is a crucial enzyme for the virulence and survival of Mycobacterium tuberculosis (M. tb) during infection. It is a key enzyme of the glyoxylate shunt and the methylcitrate cycle, metabolic pathways that are central to the bacteria’s carbon and lipid metabolism. The absence of ICL in mammals makes it a potential inhibition target for developing new treatments against tuberculosis. In M. tb, ICL exists in two isoforms, ICL1 and ICL2. Although numerous biochemical studies have been conducted to study M. tb ICL since the publication of the first ICL1 structure in 2000, key questions regarding the role of the two M. tb ICL isoforms and their modulation remain unresolved. The work described in this thesis investigates the regulation of ICL from structural and mechanistic perspectives. In particular, it focuses on the inhibition of M. tb ICL by the human macrophage metabolite itaconate, and the activation of M. tb ICL2 by lipid metabolite acetyl-coenzyme A (acetyl-CoA) and its structural analogues. The interactions between host and pathogen are important for M. tb as the bacteria may reside inside its human host for decades. Human macrophages produce itaconate as an antimicrobial metabolite. Previous studies have shown that it may act as an inhibitor of ICL, although its mode of action is not known. In this work, by using protein X-ray crystallography, mass spectrometry and mutagenesis, it was demonstrated that itaconate binds covalently to the active site cysteine of both M. tb ICL1 and ICL2. In addition, it was found that the presence of the ICL reaction product, glyoxylate, may enhance the rate of covalent modification. This work not only provides important structural information about the design of covalent ICL inhibitors, but it also provides insights into the catalytic mechanism of the enzyme, in particular the ‘back reaction’ that converts glyoxylate and succinate to itaconate. Hampered by the lack of structural information, the biological rol…
author: Kwai, Brooke X.C.
license: https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm
date published: 2022
date modified: 2026-07-24T01:02:40Z
provider: University of Auckland
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: ResearchSpace@Auckland

PropertyValue
property ID: Handle
value: https://hdl.handle.net/2292/61032