Pyruvate dehydrogenase system includes pyruvate decarboxylase, dihydrolipoic acid acetyltransferase with TPP as coenzyme, dihydrolipoic acid dehydrogenase with dihydrolipoic acid and coenzyme A, NAD? .
This enzyme system plays a key role in the tricarboxylic acid cycle, converting pyruvate into acetyl coenzyme A, which is an irreversible reaction. Acetyl coenzyme A is the intermediate of many important chemical reactions in organisms, such as the synthesis of fatty acids and cholesterol.
α -ketoglutarate dehydrogenase catalyzes oxidative decarboxylation of α -ketoglutarate to produce succinyl-CoA. This reaction needs NAD? As a hydrogen acceptor. α -ketoglutarate dehydrogenase plays a key role in the energy metabolism of organisms. Together with pyruvate dehydrogenase, it forms a part of the tricarboxylic acid cycle and is the main way of oxidation energy supply for organisms.
The activities of these enzymes are regulated by many factors, including substrate concentration, product concentration, metabolic state of metabolites, hormone regulation and so on. The activity of pyruvate dehydrogenase is influenced by acetyl coenzyme A and NADH. This is because when the substrate concentration is high, these products will inhibit the activity of enzymes, thus preventing pyruvate from over-oxidation.
ATP can also inhibit the activity of pyruvate dehydrogenase, because ATP can interact with NAD as an energy source? Competitive acetyl coenzyme A provides energy for pyruvate, so high concentration of ATP will inhibit the activity of pyruvate dehydrogenase.
Effects of enzymes on people:
1. Enzymes participate in the digestion and absorption of food: Enzymes in oral cavity and intestine can decompose protein in food, making it more easily absorbed and utilized by human body.
Salivary amylase in saliva decomposes starch into maltose, pepsin in gastric juice decomposes protein into small peptides and amino acids, and trypsin in small intestine decomposes protein into amino acids, which promotes the digestion of fat and sugar. These enzymes play a key role in the process of digestion and absorption, ensuring that the body can make full use of nutrients in food.
2. Enzymes participate in metabolic process: Enzymes play a key role in energy metabolism, substance synthesis and decomposition. For example, glycolytic enzymes break down glucose into pyruvate to provide energy for the body; Lipase decomposes fat into glycerol and fatty acids, which provide energy for the body and are also raw materials for synthesizing other substances.
Fructose-6-phosphate was converted into fructose-1, 6- diphosphate by phosphofructose kinase involved in gluconeogenesis. The role of these enzymes in the metabolic process ensures the normal functioning of various physiological functions of the body.