The biochemistry behind tuberculosis

The biochemistry behind tuberculosis

The latest breakthrough in the fight against tuberculosis (Tb) comes at an atomic level by a PhD student.

Celia Webby, a PhD student in the University’s Institute of Fundamental Sciences, has solved the atomic structure of an enzyme that the Tb bacterium needs to survive. This will pave the way for future developments in new antibiotics to fight the disease.

Ms Webby is under the supervision of Associate Professor Emily Parker and Professor Ted Baker, director of the Centre for Molecular Biodiscovery at the University of Auckland. The centre has several projects underway to determine the protein structure of the Tb bacterium, Mycobacterium tuberculosis, but researchers were having difficulty characterising the particular bacterial enzyme known as DAH7PS.

In order to study and describe the atomic structure of an enzyme (a type of protein), it must first be made soluble. Ms Webby had had previous success in solubilising proteins in order to purify and cultivate them in the laboratory for characterisation.

“It’s difficult to work on a protein that is not soluble because it needs to be soluble to be able to purify, characterise and grow crystals with. The Tb protein is grown in and isolated from Eschericha coli as this is a lot safer than working with the Tb bacterium,” Ms Webby says.

“Once we know what an enzyme looks like, and how it works, we can target it. What’s really exciting is that this particular enzyme is not produced in humans, making it an ideal target for anti-Tb drugs.”

She says the DAH7PS enzyme is significant to the development of antibiotics as it is essential for the virulence or spread of the bacterium that causes the disease. Professor Baker at the University of Auckland says Ms Webby’s success has helped Tb researchers understand the evolution of the enzyme, providing valuable insights into how it works and potentially how its activity could be blocked.

“The current antibiotics used to treat Tb have been around for a long time. We need more effective therapies to combat the disease and to tackle resistant strains which have developed over the years,” Professor Baker says.

Scott Walker, a PhD student in the same laboratory with Ms Webby and under the supervision of Dr Parker, is working on the chemistry of inhibitors (substances which bind to the chemically-active sites on proteins and enzymes to inhibit their activity). This recent breakthrough will allow him to take a closer look at the Tb enzyme.

Last year Mr Walker was a runner-up in the biotechnology section at the MacDiarmid Young Scientist of the Year awards, for his PhD project on the development of new classes of antibiotics. He specifically targets bacteria using chemical compounds he has designed to act as inhibitors. These inhibitors have the potential to disable the activity of bacteria that have become resistant to antibiotics, which is one of the largest problems in modern medicine.

Tuberculosis, an airborne infection that mainly affects the lungs, is classified as a “world health emergency” by the World Health Organisation. Globally, it is the most deadly and widespread major infectious diseases, claiming the lives of two to three million people a year.
New Zealand has one of the highest rates of Tb in the developed world, twice that of Australia. About 400 new cases are reported each year with the highest number in Auckland, followed by Manukau City and Wellington.

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