Inhibition of alcohol dehydrogenase by bismuth☆

Abstract

Bismuth compounds have been widely used for the treatment of ulcers and Helicobacter pylori infection, and enzyme inhibition was thought to be crucial for bismuth anti-microbial activity. We have investigated the interaction of colloidal bismuth subcitrate (CBS) with alcohol dehydrogenase and our results demonstrate that bismuth can effectively inhibit the enzyme. Kinetic analysis revealed that CBS acted as a non-competitive inhibitor of yeast alcohol dehydrogenase. Both UV-vis and fluorescence data show that interaction of CBS with the enzyme exhibits biphasic processes. Bismuth can replace only half of Zn(II) from the enzyme (i.e., about one Zn(II) per monomer). Surprisingly, binding of CBS also induces the enzyme dissociation from its native form, tetramer into dimers. The inhibition of Bi(III) on the enzyme is probably due to its direct interference with the zinc sites. This study is likely to provide an insight into the mechanism of action of bismuth drugs.

Inhibition of fumarase by bismuth(III): implications for the tricarboxylic acid cycle as a potential target of bismuth drugs in Helicobacter pylori

“…Bismuth-based triple therapy has been commonly recommended for eradicating H. pylori (Xia et al 2002). Up to now, the molecular mechanisms underlying the antimicrobial activities of bismuth remain to be fully established, albeit several possible mechanisms have been proposed: inhibition of proteases , urease (Zhang et al 2006), and alcohol dehydrogenase (Jin et al 2004); modulation of cellular oxidative stress; interference with nickel homeostasis ); inhibition of protein and cell wall synthesis, membrane function and ATP synthesis (Lambert and Midolo 1997). Our previous proteomic work observed that the level of at least four proteins, one elongation factor Ef-Tu, fumarase, two established metal-binding proteins HspA (Cun et al 2008) and NapA (Dundon et al 2001;Sun et al 2008), dramatically decreased upon Bi-IMAC enrichment from bismuth-treated cell extracts as compared to untreated cells.…”

“…Proteins were desalted into an appropriate buffer with a PD-10 column (GE Biosciences) (Ge et al 2006a, b). The free thiolate content of fumarase was determined by Ellman's method as described previously (Ellman 1959;Jin et al 2004). Fumarase was added into a 1 mM DTNB solution in 20 mM Hepes (pH 7.4) plus 100 mM NaCl to a final concentration of 2 lM.…”

“…Enzyme inhibition is supposed to play an important role in the action of bismuth-containing drugs, as the in vitro studies showed that Bi 3? can bind to the active sites of urease (Zhang et al 2006) and alcohol dehydrogenase (Jin et al 2004), resulting in the inhibition of the catalytic activities of these enzymes. Some other proposed target proteins are metallothioneins (Sun et al 1999), the histidine-rich protein Hpn (Ge et al 2006a, b), and serum proteins such as transferrin, lactoferrin and serum albumin (Sun and Szeto 2003).…”

Metallomics: An integrated biometal science

“…Bismuth has been demonstrated to inhibit several enzymes from H. pylori e.g., cytosolic alcohol degydrogenase (ADH), F1-ATPase and urease [113] . It binds to thiolate groups of yeast alcohol dehydrogenase, which gradually promotes enzyme multimer dissociation, favoring the formation of a dimer, rather than its native tetrameric arrangement [114] . Bismuth complexes were also found to efficiently inhibit urease [115] , possibly through the blocking the entry of substrate into the active cavity [116] .…”

Biological Chemistry of Antimony and Bismuth

“…The inhibition of H. pylori ADH by bismuth suggests that ADH is a potential target for the treatment of H. pylori infection. Baker's yeast alcohol dehydrogenase (YADH) was used as a model of H. pylori ADH due to the high sequence identity (47%) of conserved active sites [119]. Bi III binds to cysteine residues of YADH, as evidenced by the appearance of a characteristic UV-visible absorbance band of Bi-S at $360 nm upon addition of Bi III .…”