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Comparative analysis on the key enzymes of the glycerol cycle metabolic pathway in Dunaliella salina under osmotic stresses.

Chen H, Lu Y, Jiang JG - PLoS ONE (2012)

Bottom Line: The glycerol metabolic pathway is a special cycle way; glycerol-3-phosphate dehydrogenase (G3pdh), glycerol-3-phosphate phosphatase (G3pp), dihydroxyacetone reductase (Dhar), and dihydroxyacetone kinase (Dhak) are the key enzymes around the pathway.Dhar played a role of balancing the cycle metabolic pathway by its forward and backward reactions.Through synergy, the four enzymes worked together for the effective flow of the cycle metabolic pathways to maintain the glycerol requirements of cells in order to adapt to osmotic stress environments.

View Article: PubMed Central - PubMed

Affiliation: College of Food Bioengineering, South China University of Technology, Guangzhou, China.

ABSTRACT
The glycerol metabolic pathway is a special cycle way; glycerol-3-phosphate dehydrogenase (G3pdh), glycerol-3-phosphate phosphatase (G3pp), dihydroxyacetone reductase (Dhar), and dihydroxyacetone kinase (Dhak) are the key enzymes around the pathway. Glycerol is an important osmolyte for Dunaliella salina to resist osmotic stress. In this study, comparative activities of the four enzymes in D. salina and their activity changes under various salt stresses were investigated, from which glycerol metabolic flow direction in the glycerol metabolic pathway was estimated. Results showed that the salinity changes had different effects on the enzymes activities. NaCl could stimulate the activities of all the four enzymes in various degrees when D. salina was grown under continuous salt stress. When treated by hyperosmotic or hypoosmotic shock, only the activity of G3pdh in D. salina was significantly stimulated. It was speculated that, under osmotic stresses, the emergency response of the cycle pathway in D. salina was driven by G3pdh via its response to the osmotic stress. Subsequently, with the changes of salinity, other three enzymes started to respond to osmotic stress. Dhar played a role of balancing the cycle metabolic pathway by its forward and backward reactions. Through synergy, the four enzymes worked together for the effective flow of the cycle metabolic pathways to maintain the glycerol requirements of cells in order to adapt to osmotic stress environments.

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(NAD+)-dependent G3pdh activity in D. salina cells under different salinity stresses.(A): Cells grown chronically at various salinities; (B): Cells treated by hyperosmotic or hypoosmotic shock. Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.01). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
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pone-0037578-g002: (NAD+)-dependent G3pdh activity in D. salina cells under different salinity stresses.(A): Cells grown chronically at various salinities; (B): Cells treated by hyperosmotic or hypoosmotic shock. Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.01). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.

Mentions: The changes of forward and backward reaction activities of G3pdh in D. salina grown continuously under 0.5–2.5 M NaCl were minor, but both increased significantly when salinities increased to 3.0 and 3.5 M NaCl (Figure 2). The activities of both reactions reached highest at 3.5 M NaCl (77.16±1.97 and 30.11±0.91 U/mg, respectively), and then decreased when salinities increased to 4.0–5.0 M NaCl. When algal culture of 2.0 M NaCl was treated by hypoosmotic or hyperosmotic shock, both forward and backward reaction activities of G3pdh showed the escalating trends, but the trends were unconspicuous and the activity changes were minor on the whole. Furthermore, relative to the significant increase in activity from 0–3.5 M NaCl in continuous cultivation, both forward and backward reaction activities of G3pdh in cells treated by hypoosmotic or hyperosmotic shock remained at lower levels, less than 10 U/mg on the whole. In addition, it was found that the forward reaction activities of G3pdh were always higher than the backward reaction activities at most of treatments (Figure 2).


Comparative analysis on the key enzymes of the glycerol cycle metabolic pathway in Dunaliella salina under osmotic stresses.

Chen H, Lu Y, Jiang JG - PLoS ONE (2012)

(NAD+)-dependent G3pdh activity in D. salina cells under different salinity stresses.(A): Cells grown chronically at various salinities; (B): Cells treated by hyperosmotic or hypoosmotic shock. Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.01). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3366960&req=5

pone-0037578-g002: (NAD+)-dependent G3pdh activity in D. salina cells under different salinity stresses.(A): Cells grown chronically at various salinities; (B): Cells treated by hyperosmotic or hypoosmotic shock. Columns represent the means of three replicated studies in each sample, with the SD of the means (T test, P<0.01). The significance of the differences between the control (2.0) and test values were tested by using one-way ANOVA. *, P<0.05 vs control.
Mentions: The changes of forward and backward reaction activities of G3pdh in D. salina grown continuously under 0.5–2.5 M NaCl were minor, but both increased significantly when salinities increased to 3.0 and 3.5 M NaCl (Figure 2). The activities of both reactions reached highest at 3.5 M NaCl (77.16±1.97 and 30.11±0.91 U/mg, respectively), and then decreased when salinities increased to 4.0–5.0 M NaCl. When algal culture of 2.0 M NaCl was treated by hypoosmotic or hyperosmotic shock, both forward and backward reaction activities of G3pdh showed the escalating trends, but the trends were unconspicuous and the activity changes were minor on the whole. Furthermore, relative to the significant increase in activity from 0–3.5 M NaCl in continuous cultivation, both forward and backward reaction activities of G3pdh in cells treated by hypoosmotic or hyperosmotic shock remained at lower levels, less than 10 U/mg on the whole. In addition, it was found that the forward reaction activities of G3pdh were always higher than the backward reaction activities at most of treatments (Figure 2).

Bottom Line: The glycerol metabolic pathway is a special cycle way; glycerol-3-phosphate dehydrogenase (G3pdh), glycerol-3-phosphate phosphatase (G3pp), dihydroxyacetone reductase (Dhar), and dihydroxyacetone kinase (Dhak) are the key enzymes around the pathway.Dhar played a role of balancing the cycle metabolic pathway by its forward and backward reactions.Through synergy, the four enzymes worked together for the effective flow of the cycle metabolic pathways to maintain the glycerol requirements of cells in order to adapt to osmotic stress environments.

View Article: PubMed Central - PubMed

Affiliation: College of Food Bioengineering, South China University of Technology, Guangzhou, China.

ABSTRACT
The glycerol metabolic pathway is a special cycle way; glycerol-3-phosphate dehydrogenase (G3pdh), glycerol-3-phosphate phosphatase (G3pp), dihydroxyacetone reductase (Dhar), and dihydroxyacetone kinase (Dhak) are the key enzymes around the pathway. Glycerol is an important osmolyte for Dunaliella salina to resist osmotic stress. In this study, comparative activities of the four enzymes in D. salina and their activity changes under various salt stresses were investigated, from which glycerol metabolic flow direction in the glycerol metabolic pathway was estimated. Results showed that the salinity changes had different effects on the enzymes activities. NaCl could stimulate the activities of all the four enzymes in various degrees when D. salina was grown under continuous salt stress. When treated by hyperosmotic or hypoosmotic shock, only the activity of G3pdh in D. salina was significantly stimulated. It was speculated that, under osmotic stresses, the emergency response of the cycle pathway in D. salina was driven by G3pdh via its response to the osmotic stress. Subsequently, with the changes of salinity, other three enzymes started to respond to osmotic stress. Dhar played a role of balancing the cycle metabolic pathway by its forward and backward reactions. Through synergy, the four enzymes worked together for the effective flow of the cycle metabolic pathways to maintain the glycerol requirements of cells in order to adapt to osmotic stress environments.

Show MeSH
Related in: MedlinePlus