Expression, Purification and Characterisation of Haemophilus influenzae 3-Isopropylmalate Dehydrogenase (LeuB)

Abstract

3-isopropylmalate dehydrogenase (3IPMDH) is the third enzyme in leucine biosynthesis and a promising target for the development of broad-spectrum antibacterial agents. We report here the expression, purification and biochemical characterisation of Haemophilus influenzae 3-isopropylmalate dehydrogenase. The observed enzyme inhibition by the reaction product NADH could represent a regulatory mechanism for 3IPMDH.

Multiplication of Acidovorax citrulli in planta during infection of melon seedlings requires the ability to synthesize leucine

“…This study reports that leuB gene mutants of A. citrulli MH21, which are deficient in leucine biosynthesis, showed reduced growth rates in vivo and reduced pathogenicity on melon. The leuB gene encodes 3isopropylmalate (IPM) dehydrogenase, the third enzyme of the leucine biosynthetic pathway (Martignon et al, 2007;Chen et al, 2012). The other enzymes involved in leucine biosynthesis in bacteria are 2-IPM synthase encoded by leuA, 3-IPM isomerase (or dehydratase) encoded by leuC (large subunit) and leuD (small subunit), and the final enzyme is an aminotransferase which is encoded by the ilvE gene (Chen et al, 2012).…”

“…These authors attributed the loss of virulence to insufficient growth factors in the host that prevented the multiplication of the injected mutant to a toxic level (Bacon et al, 1950;Hondalus et al, 2000). Since these early studies, several auxotrophic mutants of Haemophilus influenzae, Mycobacterium tuberculosis and Corynebacterium pseudotuberculosis have been reported to be attenuated for growth in their host tissue and in virulence to the host (Simmons et al, 1997;Hondalus et al, 2000;Martignon et al, 2007). In plant pathogens, several metabolic mutants including histidine, leucine, valine, isoleucine and tryptophan purine synthesis in Pseudomonas syringae pv.…”