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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

The effect of hydrolysis of albumin on Antioxidant Capacity (AC) and Response Surplus (RS).The antioxidant capacity of albumin was increased with the hydrolysis procedure with Proteinase K (PK). However, the magnitude of the antioxidant capacity before 15 minutes and 60 minutes (total hydrolysis) of incubation with PK were only 1.2 and 1.4 times the combined original antioxidant capacity of albumin and PK without incubation (t = 0). The Antioxidant Capacity Accumulated (ACA %) appears above the bars and corresponds to 0, 15 and 60 minutes of incubation time respectively. RS values correspond to ACA % - 100 as specified in the Material and Methods section. Results are expressed as mean ± SD (n = 5). *P<0.05 vs. native albumin.
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pone-0008971-g004: The effect of hydrolysis of albumin on Antioxidant Capacity (AC) and Response Surplus (RS).The antioxidant capacity of albumin was increased with the hydrolysis procedure with Proteinase K (PK). However, the magnitude of the antioxidant capacity before 15 minutes and 60 minutes (total hydrolysis) of incubation with PK were only 1.2 and 1.4 times the combined original antioxidant capacity of albumin and PK without incubation (t = 0). The Antioxidant Capacity Accumulated (ACA %) appears above the bars and corresponds to 0, 15 and 60 minutes of incubation time respectively. RS values correspond to ACA % - 100 as specified in the Material and Methods section. Results are expressed as mean ± SD (n = 5). *P<0.05 vs. native albumin.

Mentions: Experiments to explore the effect of proteolysis and hence the structural integrity of the AC and RS of albumin showed that AC is increased as a result of hydrolytic activity of proteinase K (Figure 4). However, it was clear that the magnitude of the response was partial compared to the result observed for normal albumin (see Figure 1). Incubation of 15 minutes with proteinase K increases the AC from 187 (native) to 228 (treated) TEU (21% of RS) and 60 minutes of incubation with the proteinase K changes the AC from 187 (native) to 270 (treated) TEU (44% of RS). This means that responses of 1.21 and 1.44 times those of native albumin (including the contribution of the same proteinase K) were obtained. Although 60 minutes of incubation with proteinase K virtually totally hydrolyzed the albumin in the experimental conditions used, the maximum antioxidant capacity achieved in this way does not explain the magnitude of the change in AC reached with stressors like Reactive Oxygen Species (ROS) and UV light (Figure 1). It is possible to suppose that with the hydrolysis reactive residues from the structure of a protein such as the SHs groups could be liberated, promoting reactions of these with free radicals as described in the next section. In any case, these results implied that structural molecular integrity is important to proteins if they work as antioxidants (AC) and when they face a stressor (RS).


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)

The effect of hydrolysis of albumin on Antioxidant Capacity (AC) and Response Surplus (RS).The antioxidant capacity of albumin was increased with the hydrolysis procedure with Proteinase K (PK). However, the magnitude of the antioxidant capacity before 15 minutes and 60 minutes (total hydrolysis) of incubation with PK were only 1.2 and 1.4 times the combined original antioxidant capacity of albumin and PK without incubation (t = 0). The Antioxidant Capacity Accumulated (ACA %) appears above the bars and corresponds to 0, 15 and 60 minutes of incubation time respectively. RS values correspond to ACA % - 100 as specified in the Material and Methods section. Results are expressed as mean ± SD (n = 5). *P<0.05 vs. native albumin.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2813298&req=5

pone-0008971-g004: The effect of hydrolysis of albumin on Antioxidant Capacity (AC) and Response Surplus (RS).The antioxidant capacity of albumin was increased with the hydrolysis procedure with Proteinase K (PK). However, the magnitude of the antioxidant capacity before 15 minutes and 60 minutes (total hydrolysis) of incubation with PK were only 1.2 and 1.4 times the combined original antioxidant capacity of albumin and PK without incubation (t = 0). The Antioxidant Capacity Accumulated (ACA %) appears above the bars and corresponds to 0, 15 and 60 minutes of incubation time respectively. RS values correspond to ACA % - 100 as specified in the Material and Methods section. Results are expressed as mean ± SD (n = 5). *P<0.05 vs. native albumin.
Mentions: Experiments to explore the effect of proteolysis and hence the structural integrity of the AC and RS of albumin showed that AC is increased as a result of hydrolytic activity of proteinase K (Figure 4). However, it was clear that the magnitude of the response was partial compared to the result observed for normal albumin (see Figure 1). Incubation of 15 minutes with proteinase K increases the AC from 187 (native) to 228 (treated) TEU (21% of RS) and 60 minutes of incubation with the proteinase K changes the AC from 187 (native) to 270 (treated) TEU (44% of RS). This means that responses of 1.21 and 1.44 times those of native albumin (including the contribution of the same proteinase K) were obtained. Although 60 minutes of incubation with proteinase K virtually totally hydrolyzed the albumin in the experimental conditions used, the maximum antioxidant capacity achieved in this way does not explain the magnitude of the change in AC reached with stressors like Reactive Oxygen Species (ROS) and UV light (Figure 1). It is possible to suppose that with the hydrolysis reactive residues from the structure of a protein such as the SHs groups could be liberated, promoting reactions of these with free radicals as described in the next section. In any case, these results implied that structural molecular integrity is important to proteins if they work as antioxidants (AC) and when they face a stressor (RS).

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