title: Interactions between carbamyl phosphate synthase-I-mitochondrial aspartate aminotransferase and palmitoyl-CoA.
abstract: Carbamyl phosphate synthase-I and glutamate dehydrogenase both form a complex with mitochondrial aspartate aminotransferase. Instead of these two enzymes competing for the aminotransferase, carbamyl phosphate synthase-I enhances glutamate dehydrogenase-aminotransferase interaction. This suggests that a complex can be formed between all three enzymes. Since this complex is stable in the presence of substrates and modifiers of the three enzymes, it could conceivably convert NH+4 produced from aspartate into carbamyl phosphate. Furthermore, since carbamyl phosphate synthase-I is the predominant protein in liver mitochondria, it could play a major role in placing the aminotransferase and glutamate dehydrogenase in close proximity. Malate removes glutamate dehydrogenase from the tri-enzyme complex and thus could play a role in determining whether glutamate dehydrogenase interacts with carbamyl phosphate synthase-I or is available to participate in reactions with the Krebs cycle. Palmitoyl-CoA has a high affinity for both carbamyl phosphate synthase-I and glutamate dehydrogenase. ATP and malate which, respectively, decrease and enhance binding of palmitoyl-CoA to glutamate dehydrogenase, respectively decrease and enhance the ability of this enzyme to compete with carbamyl phosphate synthase-I for palmitoyl-CoA. Since carbamyl phosphate synthase-I is present in high levels in liver mitochondria and has a high affinity for palmitoyl-CoA, it could play a major role as a reservoir for palmitoyl-CoA.
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D001219:Aspartate Aminotransferases / Q000378:metabolism*; D001667:Binding, Competitive; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000378:metabolism*; D002417:Cattle; D055598:Chemical Phenomena; D011232:Chemical Precipitation; D002621:Chemistry; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D008025:Ligases / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000201:enzymology*; D010171:Palmitoyl Coenzyme A / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats
chemical_list: D000214:Acyl Coenzyme A; D010171:Palmitoyl Coenzyme A; D011092:Polyethylene Glycols; D005969:Glutamate Dehydrogenase; D001219:Aspartate Aminotransferases; D008025:Ligases; D002222:Carbamoyl-Phosphate Synthase (Ammonia)