Relevance
Background
Mycobacterium tuberculosis is a respiratory infection that causes numerous fatalities throughout the world. It lives in organisms and feeds off of host cells, which indicate a variety of lipases exist within M. tuberculosis. Current drugs that are on the market now target a small number of bacterial processes like cell wall formation and chromosomal replication. Although several antibiotics exist, all of them target these same mechanisms of inhibition. These commonalities have led to the prevalence of different multi-drug resistant (MDR) tuberculosis strains. Due to the high level of resistance, finding a lasting treatment for MDR TB infections has become very problematic. Studies into new mechanisms of inhibition will be crucial to prevent widespread outbreaks.
Clinical Implications
Isocitrate lyase plays a key role in survival of M. tuberculosis by sustaining intracellular infections in inflammatory respiratory macrophages. Used in the citric acid cycle, isocitrate lyase is the first enzyme catalyzing the carbon conserving glyoxylate pathway. This glyoxylate pathway has not been observed in mammals and thus presents a unique drug target to solely attack TB infections.
Protein Structure
Crystal Structure
Figure 1. Structure of Isocitrate Lyase. Quaternary structure is comprised of four subunits forming an alpha/beta barrel.
Isocitrate lyase is a tetramer with 222 symmetry. Each subunit is composed of 14 alpha helices and 14 beta sheets. A unique structural feature of this enzyme is a phenomenon called "helix swapping" GREEN BUTTON.
Function
Structural highlights
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