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Objective: To investigate enzymatic reactive aldehyde-scavenging enzyme capacity together with lipid peroxidation as expression of oxidative stress in atherosclerotic plaques of cigarette smokers and nonsmokers., Methods: We have assessed specific enzymatic activities of class 1, 2, and 3 aldehyde dehydrogenase (ALDH1, ALDH2, and ALDH3, respectively), glutathione S-transferase (isozyme A4-4, GSTA4-4), and aldose reductase (AR), namely the major reactive aldehyde-scavenging enzymes, together with lipid peroxidation, i.e., fluorescent damage products of lipid peroxidation (FDPL), in carotid atherosclerotic plaques surgically removed from 17 cigarette smokers and 17 nonsmokers., Results: The enzymatic activities of ALDH1 plus ALDH2, ALDH3, GSTA4-4, and AR were significantly lower in the atherosclerotic plaques of smokers than in those of nonsmokers, while plaque FDPL levels were significantly higher in the smokers than in the nonsmokers. The amount of cigarette smoking was correlated inversely with the aforementioned plaque enzymatic activities and directly with plaque FDPL content. Plaque FDPL levels were inversely correlated with plaque enzymatic activities in smokers and nonsmokers. The degree of carotid atherosclerotic stenosis, as expression of atherosclerosis severity, was correlated inversely with plaque enzymatic activities and directly with plaque FDPL levels in smokers and nonsmokers; moreover, the degree of carotid stenosis was directly correlated with the amount of cigarette smoking., Conclusion: atherosclerotic lesions of cigarette smokers are endowed with a depressed enzymatic reactive aldehyde-scavenging capacity eventually favoring oxidative stress and the severity of atherosclerosis., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

Xi class glutathione transferases (GSTs) are a recently identified group, within this large superfamily of enzymes, specifically endowed with glutathione-dependent reductase activity on glutathionyl-hydroquinone. Enzymes belonging to this group are widely distributed in bacteria, fungi, and plants but not in higher eukaryotes. Xi class GSTs are also frequently found in archaea and here we focus on the enzyme produced by the extreme haloalkaliphilic archaeon Natrialba magadii (NmGHR). We investigated its function and stability and determined its 3D structure in the apo form by X-ray crystallography. NmGHR displays the same fold of its mesophilic counterparts, is enriched in negatively charged residues, which are evenly distributed along the surface of the protein, and is characterized by a peculiar distribution of hydrophobic residues. A distinctive feature of haloalkaliphilic archaea is their preference for γ-glutamyl-cysteine over glutathione as a reducing thiol. Indeed we found that the N. magadii genome lacks a gene coding for glutathione synthase. Analysis of NmGHR structure suggests that the thiol binding site (G-site) of the enzyme is well suited for hosting γ-glutamyl-cysteine. [ABSTRACT FROM AUTHOR]