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The L-arginine biosynthesis pathway consists of eight enzymes that catalyse the conversion of L-glutamate to L-arginine. Arginine auxotrophs (argB/argF deletion mutants) of Mycobacterium tuberculosis are rapidly sterilised in mice, while inhibition of ArgJ with Pranlukast was found to clear chronic M. tuberculosis infection in a mouse model. Enzymes in the arginine biosynthetic pathway have therefore emerged as promising targets for anti-tuberculosis drug discovery. In this work, the ligandability of four enzymes of the pathway ArgB, ArgC, ArgD and ArgF is assessed using a fragment-based approach. We identify several hits against these enzymes validated with biochemical and biophysical assays, as well as X-ray crystallographic data, which in the case of ArgB were further confirmed to have on-target activity against M. tuberculosis. These results demonstrate the potential for more enzymes in this pathway to be targeted with dedicated drug discovery programmes.

Acetylornithine aminotransferase (AcOAT) is a type I pyridoxal 5′-phosphate-dependent enzyme catalyzing the conversion of N-acetylglutamic semialdehyde to N-acetylornithine in the presence of α-ketoglutarate, a step involved in arginine metabolism. In Escherichia coli, the biosynthetic AcOAT also catalyzes the conversion of N-succinyl-l-2-amino-6-oxopimelate to N-succinyl-l,l-diaminopimelate, one of the steps in lysine biosynthesis. It is closely related to ornithine aminotransferase. AcOAT was cloned from Salmonella typhimurium and E. coli, overexpressed in E. coli and purified using Ni–NTA affinity column chromatography. The enzymes crystallized in the presence of gabaculine. Crystals of E. coli AcOAT (eAcOAT) only diffracted X-rays to 3.5 Å and were twinned. The crystals of S. typhimurium AcOAT (sAcOAT) diffracted to 1.9 Å and had a dimer in the asymmetric unit. The structure of sAcOAT was solved by the molecular-replacement method. [ABSTRACT FROM AUTHOR]

The L-arginine biosynthesis pathway consists of eight enzymes that catalyse the conversion of L-glutamate to L-arginine. Arginine auxotrophs (argB/argF deletion mutants) of Mycobacterium tuberculosis are rapidly sterilised in mice, while inhibition of ArgJ with Pranlukast was found to clear chronic M. tuberculosis infection in a mouse model. Enzymes in the arginine biosynthetic pathway have therefore emerged as promising targets for anti-tuberculosis drug discovery. In this work, the ligandability of four enzymes of the pathway ArgB, ArgC, ArgD and ArgF is assessed using a fragment-based approach. We identify several hits against these enzymes validated with biochemical and biophysical assays, as well as X-ray crystallographic data, which in the case of ArgB were further confirmed to have on-target activity against M. tuberculosis . These results demonstrate the potential for more enzymes in this pathway to be targeted with dedicated drug discovery programmes., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2021 The Author(s).)