Inhibition studies of ketol-acid reductoisomerases from pathogenic microorganisms
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
Authors: Wun, Shun Jie; Johnson, Lambro A.; You, Lv; McGeary, Ross P.; Brueck, Thomas; Schenk, Gerhard; Guddat, Luke W.
Abstract
Ketol-acid reductoisomerase (KARI), the second enzyme in the branched-chain amino acid (BCAA) biosynthesis pathway, is an emerging target for the discovery of biocides. Here, we demonstrate that cyclopropane-1,1-dicarboxylate (CPD) inhibits KARIs from the pathogens Mycobacterium tuberculosis (Mt) and Campylobacter jejuni (Cj) reversibly with K-i values of 3.03 mu M and 0.59 mu M, respectively. Another reversible inhibitor of both KARIs, Hoe 704, is more potent than CPD with K-i values of 300 nM and 110 nM for MtKARI and CjKARI, respectively. The most potent inhibitor tested here is N-hydroxy-N-isopropyloxamate (IpOHA). It has a K-i of similar to 26 nM for MtKARI, but binds rather slowly (k(on) similar to 900 M(-1)s(-1)). In contrast, IpOHA binds more rapidly (k(on) similar to 7000 M(-1)s(-1)) to CjKARI and irreversibly.
Does Mycobacterium bovis persist in cattle in a non-replicative latent state as Mycobacterium tuberculosis in human beings?
VETERINARY MICROBIOLOGY
Authors: Garcia, Julia Sabio Y.; Bigi, Maria M.; Klepp, Laura, I; Garcia, Elizabeth A.; Blanco, Federico C.; Bigi, Fabiana
Abstract
Members of the Mycobacterium tuberculosis complex (MTBC) are responsible for tuberculosis in several mammals. In this complex, Mycobacterium tuberculosis and Mycobacterium bovis, which are closely related, show host preference for humans and cattle, respectively. Although human and bovine tuberculosis are clinically similar, M. tuberculosis mostly causes latent infection in humans, whereas M. bovis frequently leads to an acute infection in cattle. This review attempts to connect the pathology in experimental animal models as well as the cellular responses to M. bovis and M. tuberculosis regarding the differences in protein expression and regulatory mechanisms of both pathogens that could explain their apparent divergent latency behaviour. The occurrence of latent bovine tuberculosis (bTB) would represent a serious complication for the eradication of the disease in cattle, with the risk of onward transmission to humans. Thus, understanding the physiological events that may lead to the state of latency in bTB could assist in the development of appropriate prevention and control tools.