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Protein antioxidant response to the stress and the relationship between molecular structure and antioxidant function.

Medina-Navarro R, Durán-Reyes G, Díaz-Flores M, Vilar-Rojas C - PLoS ONE (2010)

Bottom Line: Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems.However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin.The data presented show the significant antioxidant behavior of proteins and demonstrate the existence of a previously unrecognized antioxidant response to the stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Metabolism, Center for Biomedical Research of Michoacán, Morelia, Michoacán, México. rafael.medina@imss.gob.mx

ABSTRACT

Background: Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems. However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin. It is leading to new concepts that even consider albumin not only as an antioxidant but as the major antioxidant in plasma known to be exposed to continuous oxidative stress. Evidence presented here establishes a previously unrecognized relationship between proteins' antioxidant capacity and structural stress.

Methodology/principal findings: A chemiluminiscence based antioxidant assay was achieved to quantify the antioxidant capacity of albumin and other proteins. The capabilities of proteins as antioxidants were presented, but in addition a new and powerful component of the protein antioxidant capacity was discovered. The intrinsic component, designated as Response Surplus (RS), represents a silent reserve of antioxidant power that awakens when proteins face a structural perturbation (stressor) such as temperature, short wave UV light, the same reactive oxygen species, and more extreme changes like glucose or aldehyde-mediated structural modifications. The work also highlights the importance of structural changes in protein antioxidant properties and the participation of sulfhydryl groups (SHs) in the RS antioxidant component. Based on recent evidence about the SH group chemistry, a possible model for explaining RS is proposed.

Conclusions/significance: The data presented show the significant antioxidant behavior of proteins and demonstrate the existence of a previously unrecognized antioxidant response to the stress. Several implications, including changes in elementary concepts about antioxidants and protein function, should emerge from here.

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Related in: MedlinePlus

Response Surplus (RS) produced by albumin modified by acrolein and glucose.Structural modifications introduced by acrolein and glucose impaired the RS of the protein by a high magnitude. Normal albumin exposed to UV light responds to the stressor with an increase of 8 and up to 11 times the base value (100%) even before 1 and 3 minutes of exposure respectively (ACA% = 800% and 1100%). In contrast, samples of albumin modified with acrolein and partially glycated respond with increases of 2.2 and 3.2 times the base value of 100%. Base value corresponds to the Antioxidant Capacity average before exposure to UV light, and appears as 100% in the graph. Results are expressed as mean ± SD (n = 5). *P<0.005 vs. albumin control; **P<0.001 vs. native albumin. 1 Partially glycated as described in the Material and Methods section.
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pone-0008971-g009: Response Surplus (RS) produced by albumin modified by acrolein and glucose.Structural modifications introduced by acrolein and glucose impaired the RS of the protein by a high magnitude. Normal albumin exposed to UV light responds to the stressor with an increase of 8 and up to 11 times the base value (100%) even before 1 and 3 minutes of exposure respectively (ACA% = 800% and 1100%). In contrast, samples of albumin modified with acrolein and partially glycated respond with increases of 2.2 and 3.2 times the base value of 100%. Base value corresponds to the Antioxidant Capacity average before exposure to UV light, and appears as 100% in the graph. Results are expressed as mean ± SD (n = 5). *P<0.005 vs. albumin control; **P<0.001 vs. native albumin. 1 Partially glycated as described in the Material and Methods section.

Mentions: The evidence indicates that the protein modifiers used here increase the antioxidant capacity of the albumin (Figure 8). The structural changes produced by protein-acrolein adduct formation and the non-enzymatic attachment of glucose to free primary amine residues seem to be stressors capable of inducing an incipient antioxidant response, increasing the AC by up to 4 times the native albumin. In contrast, these same changes produced a drastic reduction in the RS of the albumin (Figure 9) when it was previously challenged with the exposure of UV light (254 nm). One minute of exposure to UV light increased the ACA % 8 times, to 800%, whereas albumin treated previously with acrolein and glycosilated albumin in the same conditions increased the ACA % by only 1.9 and 2 times respectively (ACA% = 190 and 200%). When the previous exposure time to UV light was increased to 3 minutes native albumin reached more than 11 times the antioxidant capacity of native albumin (ACA% = 1100), whereas acrolein-modified and glycosilated albumin achieved only 2.2 and 3.2 times the antioxidant capacity presented before UV exposure (ACA% = 220 and 320% respectively). The results previously described emphasized the importance and complexities of the relationship between antioxidant behavior and the protein structure, which produce a partial increase but a remarkable total decrease of protein antioxidant capacity.


Protein antioxidant response to the stress and the relationship between molecular structure and antioxidant function.

Medina-Navarro R, Durán-Reyes G, Díaz-Flores M, Vilar-Rojas C - PLoS ONE (2010)

Response Surplus (RS) produced by albumin modified by acrolein and glucose.Structural modifications introduced by acrolein and glucose impaired the RS of the protein by a high magnitude. Normal albumin exposed to UV light responds to the stressor with an increase of 8 and up to 11 times the base value (100%) even before 1 and 3 minutes of exposure respectively (ACA% = 800% and 1100%). In contrast, samples of albumin modified with acrolein and partially glycated respond with increases of 2.2 and 3.2 times the base value of 100%. Base value corresponds to the Antioxidant Capacity average before exposure to UV light, and appears as 100% in the graph. Results are expressed as mean ± SD (n = 5). *P<0.005 vs. albumin control; **P<0.001 vs. native albumin. 1 Partially glycated as described in the Material and Methods section.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2813298&req=5

pone-0008971-g009: Response Surplus (RS) produced by albumin modified by acrolein and glucose.Structural modifications introduced by acrolein and glucose impaired the RS of the protein by a high magnitude. Normal albumin exposed to UV light responds to the stressor with an increase of 8 and up to 11 times the base value (100%) even before 1 and 3 minutes of exposure respectively (ACA% = 800% and 1100%). In contrast, samples of albumin modified with acrolein and partially glycated respond with increases of 2.2 and 3.2 times the base value of 100%. Base value corresponds to the Antioxidant Capacity average before exposure to UV light, and appears as 100% in the graph. Results are expressed as mean ± SD (n = 5). *P<0.005 vs. albumin control; **P<0.001 vs. native albumin. 1 Partially glycated as described in the Material and Methods section.
Mentions: The evidence indicates that the protein modifiers used here increase the antioxidant capacity of the albumin (Figure 8). The structural changes produced by protein-acrolein adduct formation and the non-enzymatic attachment of glucose to free primary amine residues seem to be stressors capable of inducing an incipient antioxidant response, increasing the AC by up to 4 times the native albumin. In contrast, these same changes produced a drastic reduction in the RS of the albumin (Figure 9) when it was previously challenged with the exposure of UV light (254 nm). One minute of exposure to UV light increased the ACA % 8 times, to 800%, whereas albumin treated previously with acrolein and glycosilated albumin in the same conditions increased the ACA % by only 1.9 and 2 times respectively (ACA% = 190 and 200%). When the previous exposure time to UV light was increased to 3 minutes native albumin reached more than 11 times the antioxidant capacity of native albumin (ACA% = 1100), whereas acrolein-modified and glycosilated albumin achieved only 2.2 and 3.2 times the antioxidant capacity presented before UV exposure (ACA% = 220 and 320% respectively). The results previously described emphasized the importance and complexities of the relationship between antioxidant behavior and the protein structure, which produce a partial increase but a remarkable total decrease of protein antioxidant capacity.

Bottom Line: Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems.However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin.The data presented show the significant antioxidant behavior of proteins and demonstrate the existence of a previously unrecognized antioxidant response to the stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Metabolism, Center for Biomedical Research of Michoacán, Morelia, Michoacán, México. rafael.medina@imss.gob.mx

ABSTRACT

Background: Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems. However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin. It is leading to new concepts that even consider albumin not only as an antioxidant but as the major antioxidant in plasma known to be exposed to continuous oxidative stress. Evidence presented here establishes a previously unrecognized relationship between proteins' antioxidant capacity and structural stress.

Methodology/principal findings: A chemiluminiscence based antioxidant assay was achieved to quantify the antioxidant capacity of albumin and other proteins. The capabilities of proteins as antioxidants were presented, but in addition a new and powerful component of the protein antioxidant capacity was discovered. The intrinsic component, designated as Response Surplus (RS), represents a silent reserve of antioxidant power that awakens when proteins face a structural perturbation (stressor) such as temperature, short wave UV light, the same reactive oxygen species, and more extreme changes like glucose or aldehyde-mediated structural modifications. The work also highlights the importance of structural changes in protein antioxidant properties and the participation of sulfhydryl groups (SHs) in the RS antioxidant component. Based on recent evidence about the SH group chemistry, a possible model for explaining RS is proposed.

Conclusions/significance: The data presented show the significant antioxidant behavior of proteins and demonstrate the existence of a previously unrecognized antioxidant response to the stress. Several implications, including changes in elementary concepts about antioxidants and protein function, should emerge from here.

Show MeSH
Related in: MedlinePlus