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Pyruvate carboxylase (PC) encoded by the gene PC is an enzyme (EC 6.4.1.1) of the ligase class that catalyzes (depending on the species) the physiologically irreversible [citation needed] carboxylation of pyruvate to form oxaloacetate (OAA).
Firstly the oxaloacetate is reduced to malate using NADH. Then the malate is decarboxylated to pyruvate. Now this pyruvate can easily enter the mitochondria, where it is carboxylated again to oxaloacetate by pyruvate carboxylase. In this way, the transfer of acetyl-CoA that is from the mitochondria into the cytoplasm produces a molecule of NADH.
d -Glucose + 2 [NAD] + + 2 [ADP] + 2 [P] i 2 × Pyruvate 2 × + 2 [NADH] + 2 H + + 2 [ATP] + 2 H 2 O Glycolysis pathway overview The use of symbols in this equation makes it appear unbalanced with respect to oxygen atoms, hydrogen atoms, and charges. Atom balance is maintained by the two phosphate (P i) groups: Each exists in the form of a hydrogen phosphate anion, dissociating to contribute ...
Enzyme-bound pyridoxamine in turn reacts with pyruvate, oxaloacetate, or alpha-ketoglutarate, giving alanine, aspartic acid, or glutamic acid, respectively. Many transamination reactions occur in tissues, catalysed by transaminases specific for a particular amino/keto acid pair.
Malate, in the mitochondrial matrix, can be used to make pyruvate (catalyzed by malic enzyme) or oxaloacetic acid, both of which can enter the citric acid cycle. Glutamine can also be used to produce oxaloacetate during anaplerotic reactions in various cell types through "glutaminolysis," which is also seen in many c-Myc transformed cells. [3]
The others are NADP-malic enzyme and NAD-malic enzyme. [17] [18] In C 4 carbon fixation, carbon dioxide is first fixed by combination with phosphoenolpyruvate to form oxaloacetate in the mesophyll. In PEPCK-type C 4 plants the oxaloacetate is then converted to aspartate, which travels to the bundle sheath.
The oxaloacetate is returned to the mitochondrion as malate (and then converted back into oxaloacetate to transfer more acetyl-CoA out of the mitochondrion). [19] This cytosolic acetyl-CoA can then be used to synthesize fatty acids through carboxylation by acetyl-CoA carboxylase into malonyl CoA , the first committed step in the synthesis of ...
Both malate and oxaloacetate can be converted into phosphoenolpyruvate, which is the product of phosphoenolpyruvate carboxykinase, the first enzyme in gluconeogenesis. The net result of the glyoxylate cycle is therefore the production of glucose from fatty acids.