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The enzymatic steps in urea synthesis


, : The enzymatic steps in urea synthesis. Journal of Biological Chemistry 172(2): 405-415

Further studies in the synthesis of arginine from citrulline, and citrulline from ornithine, have been carried out with tissue homogenate fractions obtained by differential centrifugation. The enzyme system catalyzing the citrulline-arginine reaction has been resolved into 2 parts, a soluble synthesizing enzyme fraction and an insoluble hydrogen transport fraction which appears to include the cytochrome system. The enzyme system catalyzing the ornithine-citrulline reaction is associated with the insoluble residue of the liver cell. Supplementation of the residue with Mg ions in addition to the requirements prescribed for the whole homogenate system is necessary for optimum activity. Both AMP and ATP are almost equally effective with residue. The significance of these findings in relation to the Krebs-Henseleit urea cycle is discussed.

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PMID: 18901157


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