Final answer:
No external reducing agent is required for GST-DHFR-His as it involves enzymes that naturally participate in redox reactions within metabolic pathways. Succinate dehydrogenase supports the TCA cycle and electron transport chain, while phosphoglycerate kinase is involved in glycolysis and can influence the production of antipathogenic compounds.
Step-by-step explanation:
Role of Succinate Dehydrogenase and Phosphoglycerate Kinase in Plant Metabolism
Succinate dehydrogenase (SDH) or succinate-coenzyme Q reductase (SQR) is an enzyme that participates in both the citric acid cycle and the mitochondrial electron transport chain. It catalyzes the oxidation of succinate to fumarate with the simultaneous reduction of FAD (flavin adenine dinucleotide) to FADH₂. The mention of GST-DHFR-His, which likely refers to a fusion protein involving Glutathione S-transferase and dihydrofolate reductase with a histidine tag for purification purposes, suggests that no external reducing agent is required since the enzyme itself is part of a redox reaction, naturally maintaining its reduced state through its normal functioning within the metabolic pathways.
Conversely, phosphoglycerate kinase is a key enzyme in the glycolysis pathway, catalyzing the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate and generating ATP in the process. Changes in the expression of this enzyme and others related to the glycolytic pathway can redirect metabolic flux towards the pentose phosphate pathway. This pathway generates important intermediates for the biosynthesis of antipathogenic compounds like isoprenoids, which are vital for plant defense mechanisms.