alpha-Glucan biosynthesis and the GlgE pathway in Mycobacterium tuberculosis

It has long been reported that Mycobacterium tuberculosis is capable of synthesizing the alpha-glucan glycogen. However, what makes this bacterium stand out is that it coats itself in a capsule that mainly consists of a glycogen-like alpha-glucan. This polymer helps the pathogen evade immune responses. In 2010, the biosynthesis of alpha-glucans has been shown to not only involve the classical enzymes of glycogen metabolism but also a distinct GlgE pathway. Since then, this pathway has attracted attention not least in terms of the quest for new inhibitors that could be developed into new treatments for tuberculosis. Some lines of recent inquiry have shed a lot of light on to how GlgE catalyses the polymerization of alpha-glucan, using alpha-maltose 1-phosphate (M1P) as a building block and how the pathways are regulated. Nevertheless, many unanswered questions remain regarding the synthesis and role of alpha-glucans in mycobacteria and the numerous other bacteria that possess the GlgE pathway.