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In biochemistry, a zymogen (/ ˈ z aɪ m ə dʒ ən,-m oʊ-/ [1] [2]), also called a proenzyme (/ ˌ p r oʊ ˈ ɛ n z aɪ m / [3] [4]), is an inactive precursor of an enzyme.A zymogen requires a biochemical change (such as a hydrolysis reaction revealing the active site, or changing the configuration to reveal the active site) for it to become an active enzyme.
Phosphoenolpyruvate carboxykinase (EC 4.1.1.32, PEPCK) is an enzyme in the lyase family used in the metabolic pathway of gluconeogenesis. It converts oxaloacetate into phosphoenolpyruvate and carbon dioxide. [1] [2] [3] It is found in two forms, cytosolic and mitochondrial.
Acetyl-CoA is a metabolic intermediate that is involved in many metabolic pathways in an organism. It is produced during the breakdown of glucose , fatty acids , and amino acids , and is used in the synthesis of many other biomolecules , including cholesterol , fatty acids , and ketone bodies .
Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and this complex links the glycolysis metabolic pathway to the citric acid cycle. Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate. [2]
Glucokinase has been found in the brain in largely the same areas that contain glucose-sensing neurons, including both of the hypothalamic nuclei. Inhibition of glucokinase abolishes the ventromedial nucleus response to a meal. However, brain glucose levels are lower than plasma levels, typically 0.5–3.5 mM.
Glyceroneogenesis is a metabolic pathway which synthesizes glycerol 3-phosphate (used to form triglycerides) from precursors other than glucose. [1] Usually, glycerol 3-phosphate is generated from glucose by glycolysis, in the liquid of the cell's cytoplasm (the cytosol).
[1]: 26 In most cases of a metabolic pathway, the product of one enzyme acts as the substrate for the next. However, side products are considered waste and removed from the cell. [2] Different metabolic pathways function in the position within a eukaryotic cell and the significance of the pathway in the given compartment of the cell. [3]
Metabolic intermediates are compounds produced during the conversion of substrates (starting molecules) into final products in biochemical reactions within cells. [1]Although these intermediates are of relatively minor direct importance to cellular function, they can play important roles in the allosteric regulation of enzymes, glycolysis, the citric acid cycle, and amino acid synthesis.