Double mode of inhibition-inducing interactions of 1,4-naphthoquinone with urease: arylation versus oxidation of enzyme thiols
Krajewska, B; Zaborska, W
| HERO ID | 1329872 |
|---|---|
| In Press | No |
| Year | 2007 |
| Title | Double mode of inhibition-inducing interactions of 1,4-naphthoquinone with urease: arylation versus oxidation of enzyme thiols |
| Authors | Krajewska, B; Zaborska, W |
| Journal | Bioorganic & Medicinal Chemistry |
| Volume | 15 |
| Issue | 12 |
| Page Numbers | 4144-4151 |
| Abstract | In their inhibition-inducing interactions with enzymes, quinones primarily utilize two mechanisms, arylation and oxidation of enzyme thiol groups. In this work, we investigated the interactions of 1,4-naphthoquinone with urease in an effort to estimate the contribution of the two mechanisms in the enzyme inhibition. Jack bean urease, a homohexamer, contains 15 thiols per enzyme subunit, six accessible under non-denaturing conditions, of which Cys592 proximal to the active site indirectly participates in the enzyme catalysis. Unlike by 1,4-benzoquinone, a thiol arylator, the inactivation of urease by 1,4-naphthoquinone under aerobic conditions was found to be biphasic, time- and concentration-dependent with a non-linear residual activity-modified thiols dependence. DTT protection studies and thiol titration with DTNB suggest that thiols are the sites of enzyme interactions with the quinone. The inactivated enzyme had approximately 40% of its activity restored by excess DTT supporting the presence of sulfenic acid resulting from the oxidation of enzyme thiols by ROS. Furthermore, the aerobic inactivation was prevented in approximately 30% by catalase, proving the involvement of hydrogen peroxide in the process. When H2O2 was directly applied to urease, the enzyme showed susceptibility to this inactivation in a time- and concentration-dependent manner with the inhibition constant of H2O2 Ki = 3.24 mM. Additionally, anaerobic inactivation of urease was performed and was found to be weaker than aerobic. The results obtained are consistent with a double mode of 1,4-naphthoquinone inhibitory action on urease, namely through the arylation of the enzyme thiol groups and ROS generation, notably H2O2, resulting in the oxidation of the groups. |
| Doi | 10.1016/j.bmc.2007.03.071 |
| Pmid | 17416528 |
| Wosid | WOS:000246870400020 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |
| Keyword | urease; 1,4-naphthoquinone; inhibition; arylation; ROS; hydrogen peroxide |