BIOCHEMICAL CHARACTERISATION OF PIMELATE BIOSYNTHETIC GENES OF Mycobacterium tuberculosis

Abstract

Emergence of drug resistant tuberculosis (TB) and comorbidity with HIV, especially in the sub-Saharan Africa and Asia, has exacerbated the problem of TB, with an estimated 1.6 million people dying of the disease worldwide in 2017 alone. This programme of work approached the problem of TB by utilising a two-pronged approach to novel drug identification.
The first approach investigated enzymes involved in pimelate biosynthesis in Mycobacterium tuberculosis (Mtb). Pimelate, the precursor of biotin synthesis in bacteria, is an essential micronutrient needed for the survival of the organism. This biochemical study identified four enzymes, Rv0089, Rv1882c, Rv3177 and Rv2715 as possible proteins involved in this pathway. Due to ongoing issues with toxicity in various expression hosts, only Rv0089 was purified and biochemical studies performed. These studies confirmed the enzyme to be a methyl transferase capable of converting S-adenosyl-methionine (SAM) into S-adenosyl-L-homocysteine (SAH) with a preference for malonyl-CoA.
The second approach analysed isoxyl and SQ109 hybrid anti-tubercular agents. A series of hybrids were synthesized to develop a potential new lead compound with multiple modes of action and decreased propensity to develop resistance. A lead compound with an MIC of 0.120 µg/mL against Mtb was successfully synthesised showing markedly higher activities than the parental drugs (SQ109 MIC = 0.48 µg/mL and isoxyl MIC = 0.24 µg/mL). Additionally, this compound was equally potent against rifampicin and isoniazid singularly resistant Mtb.
This work has therefore provided a basis by which new anti-tubercular drugs can be developed.