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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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The pathway of glycerol metabolism in Dunaliella.
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pone-0037578-g001: The pathway of glycerol metabolism in Dunaliella.

Mentions: In Dunaliella, glycerol may be synthesized via two different metabolic pathways: one using a photosynthetic product and the other via the metabolic degradation of starch in cell [2], [7], [8]. Figure 1 shows the metabolism pathway of glycerol in Dunaliella. Firstly, via glycolysis pathway the glucose synthesized from photosynthesis or hydrolyzed from starch is converted to fructose-1, 6- bisphosphate and next to dihydroxyacetone phosphate (DHAP), which is converted to glycerol-3-phosphate by glycerol-3-phosphate dehydrogenase (G3pdh). Finally, glycerol-3-phosphate is converted to glycerol by glycerol-3-phosphate phosphatase (G3pp) [9], [10]. In the pathway of glycerol degradation, excess glycerol is removed by oxidation to dihydroxyacetone (DHA) catalyzed by glycerol dehydrogenase (also known as DHA reductase, Dhar), and then DHA is converted to DHAP catalyzed by DHA kinase (Dhak) [11]–[13].


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)

The pathway of glycerol metabolism in Dunaliella.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0037578-g001: The pathway of glycerol metabolism in Dunaliella.
Mentions: In Dunaliella, glycerol may be synthesized via two different metabolic pathways: one using a photosynthetic product and the other via the metabolic degradation of starch in cell [2], [7], [8]. Figure 1 shows the metabolism pathway of glycerol in Dunaliella. Firstly, via glycolysis pathway the glucose synthesized from photosynthesis or hydrolyzed from starch is converted to fructose-1, 6- bisphosphate and next to dihydroxyacetone phosphate (DHAP), which is converted to glycerol-3-phosphate by glycerol-3-phosphate dehydrogenase (G3pdh). Finally, glycerol-3-phosphate is converted to glycerol by glycerol-3-phosphate phosphatase (G3pp) [9], [10]. In the pathway of glycerol degradation, excess glycerol is removed by oxidation to dihydroxyacetone (DHA) catalyzed by glycerol dehydrogenase (also known as DHA reductase, Dhar), and then DHA is converted to DHAP catalyzed by DHA kinase (Dhak) [11]–[13].

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