Home >> Redox Report, Volume 9, Number 1

Dihydrolipoic acid lowers the redox activity of transition metal ions but does not remove them from the active site of enzymes

Authors: Suh, Jung1; Zhu, Ben-Zhan2; deSzoeke, Evan2; Frei, Balz1; Hagen, Tory1

Source: Redox Report, Volume 9, Number 1, February 2004 , pp. 57-61(5)

Publisher: Maney Publishing

Buy & download fulltext article:

OR

Price: $48.00 plus tax (Refund Policy)

Abstract:

?-Lipoic acid (LA) and its reduced form, dihydrolipoic acid (DHLA), have been suggested to chelate transition metal ions and, hence, mitigate iron- and copper-mediated oxidative stress in biological systems. However, it remains unclear whether LA and DHLA chelate transition metal ions in a redox-inactive form, and whether they remove metal ions from the active site of enzymes. Therefore, we investigated the effects of LA and DHLA on iron- or copper-catalyzed oxidation of ascorbate, a sensitive assay for the redox activity of these metal ions. We found that DHLA, but not LA, significantly inhibited ascorbate oxidation mediated by Fe(III)-citrate, suggesting that reduced thiols are required for iron binding. DHLA also strongly inhibited Cu(II)(histidine)2-mediated ascorbate oxidation in a concentration-dependent manner, with complete inhibition at a DHLA:Cu(II) molar ratio of 3:1. In contrast, no inhibition of copper-catalyzed ascorbate oxidation was observed with LA. To investigate whether LA and DHLA remove copper or iron from the active site of enzymes, Cu,Zn superoxide dismutase and the iron-containing enzyme aconitase were used. We found that neither LA nor DHLA, even at high, millimolar concentrations, altered the activity of these enzymes. Our results suggest that DHLA chelates and inactivates redox-active transition metal ions in small-molecular, biological complexes without affecting iron- or copper-dependent enzyme activities.

Keywords: REDOX ACTIVITY; DIHYDROLIPOIC ACID; TRANSITION METALS

Document Type: Research Article

DOI: http://dx.doi.org/10.1179/135100004225003923

Affiliations: 1: Department of Biochemistry and Biophysics, Oregon State University, Corvallis, Oregon, USA 2: Linus Pauling Institute, Oregon State University, Corvallis, Oregon, USA

Publication date: 2004-02-01

Related content
Marked list

Tools

Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content

Text size:

A | A | A | A
^ Back to top
Share this item with others: These icons link to social bookmarking sites where readers can share and discover new web pages. print icon Print this page