The metabolism of L-arginine starts with the acetylation of L-glutamic acid resulting in a N-acetylglutamic acid while releasing a coenzyme A and a hydrogen ion. N-acetylglutamic acid is then phosphorylated via an ATP driven acetylglutamate kinase which yields a N-acetyl-L-glutamyl 5-phosphate. This compound undergoes a NDPH dependent reduction resulting in N-acetyl-L-glutamate 5-semialdehyde, which then reacts with L-glutamic acid through a acetylornithine aminotransferase / N-succinyldiaminopimelate aminotransferase to produce an N-acetylornithine. Next N-acetylornithine is deacetylated through a acetylornithine deacetylase yielding an ornithine. L-glutamine is used to synthesize carbamoyl phosphate through the interaction of L-glutamine, water, ATP, and hydrogen carbonate. This reaction yields ADP, L-glutamic acid, phosphate, and hydrogen ion. Carbamoyl phosphate and ornithine are used to catalyze the production of citrulline through an ornithine carbamoyltransferase. Citrulline reacts with L-aspartic acid through an ATP dependent enzyme, argininosuccinate synthase to produce pyrophosphate, AMP and argininosuccinic acid. Argininosussinic acid is then lyase to produce L-arginine and fumaric acid. L-arginine can be metabolized into succinic acid by two different sets of reactions: 1. Arginine reacts with succinyl-CoA through a arginine N-succinyltransferase resulting in N2-succinyl-L-arginine while releasing CoA and Hydrogen Ion. N2-succinyl-L-arginine is then dihydrolase to produce a N2-succinyl-L-ornithine through a N-succinylarginine dihydrolase which in turn reacts with oxoglutaric acid through succinylornithine transaminase resulting in L-glutamic acid and N2-succinyl-L-glutamic acid 5-semialdehyde. Next N2-succinyl-L-glutamic acid 5-semialdehyde reacts with a NAD dependent dehydrogenase resulting in N2-succinylglutamate and releases NADH and hydrogen ion. Finally, N2-succinylglutamate reacts with water through a succinylglutamate desuccinylase resulting in L-glutamic acid and a succinic acid. The succinic acid is then incorporated in the TCA cycle 2. Argine reacts with carbon dioxide and a hydrogen ion through a biodegradative arginine decarboxylase, resulting in Agmatine. Agmatine is transformed into putrescine by reacting with water and an agmatinase, and releasing urea. Putrescine can be metabolized by reaction with either l-glutamic acid or oxoglutaric acid. If putrescine reacts with L-glutamic acid, it reacts through an ATP mediated gamma-glutamylputrescine producing a hydrogen ion, ADP, phosphate and gamma-glutamyl-L-putrescine. Gamma-glutamyl-L-putrescine is reduced via interactions with oxygen, water and a gamma-glutamylputrescine oxidoreductase resulting in ammonium, hydrogen peroxide and 4-gamma-glutamylamino butanal. Dehydrogenated through a NADP mediated reaction lead by gamma-glutamyl-gamma-aminobutaryaldehyde dehydrogenase, 4-gamma-glutamylamino butanal is converted into hydrogen ions, NADPH and 4-glutamylamino butanoate. In turn, the latter compound reacts with water through a gamma-glutamyl-gamma-aminobutyrate hydrolase resulting in L-glutamic acid and Gamma aminobutyric acid. On the other hand, if putrescine reacts with oxoglutaric acid through a putrescine aminotransferase, it results in L-glutamic acid, and a 4-aminobutyraldehyde, which continues and reacts with water through a NAD dependent gamma aminobutyraldehyde dehydrogenase resulting in hydrogen ion, NADH and gamma-aminobutyric acid. Gamma Aaminobutyric acid reacts with oxoglutaric acid through 4-aminobutyrate aminotransferase resulting in L-glutamic acid and succinic acid semialdehyde. Succinic acid semialdehyde then reacts with either NADP or NAD to produce succinic acid through succinate-semialdehyde dehydrogenase or aldehyde dehydrogenase-like protein yneI respectively. Succinic acid can then be integrated in the TCA cycle.

Arginine Metabolism References