Enzymatische und nichtenzymatische Citrullinsynthese

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Abstract
Carbamyl compounds can be formed non-enzymatically from ornithine and carbamyl phosphate. Under conditions optimal for enzymatic catalysis non-enzymatic synthesis is slight and is never more than 5% of the total synthesis. The optimal temperature for the carbamyl transferase of ornithine is 30[degree]C. The optimal pH for carbamyl transferase lies between pH 7.3 and 8.0. The incubation period for the enzymatic reaction must not be more than 5 hours since a longer period causes an increased non-enzymatic synthesis of ureide compounds. In non-enzymatic synthesis from carbamyl phosphate and ornithine a- o -carbamylornithine is formed predominantly, along with small amounts of citrullin and [alpha]-carbamylornithine. Enzymatic synthesis gives mainly citrullin and insignificant amounts of both of the other carbamylornithines. At room temperature and at still higher temperatures the non-enzymatic synthesis of carbamylornithine compounds increases significantly; at 2-4[degree]C the reaction is completely inhibited.