What is the importance of oxidoreductases?

Oxidoreductase enzymes play crucial roles in both aerobic and anaerobic metabolic pathways. They are present in various metabolic processes such as glycolysis, oxidative phosphorylation, the TCA cycle, and amino acid metabolism. 

In glycolysis, the enzyme glyceraldehyde-3-phosphate dehydrogenase facilitates the reduction of NAD+ to NADH. This conversion generates NADH, which is crucial for energy production. To maintain the cell's redox balance, NADH needs to be re-oxidized back to NAD+. This re-oxidation occurs in the oxidative phosphorylation pathway. Additional NADH molecules are formed in the TCA cycle. 

In anaerobic glycolysis, when oxygen is limited, NADH generated in glycolysis is oxidized by reducing pyruvate to lactate. In the muscle and liver cells, lactate is further oxidized back to pyruvate, which then enters the TCA cycle for further oxidation. Moreover, most amino acids can be broken down into intermediates of the TCA cycle. This breakdown leads to the conversion of amino acid carbon skeletons into oxaloacetate, which is then converted into pyruvate. This pyruvate can subsequently be utilized in the gluconeogenic pathway to produce glucose.