Biochemistry

Second stage. Another ammonia molecule is bound to glutamic acid by reductive amination with a-ketoglutaric acid. Glutamic acid transfers the fixed ammonia molecule as an NH 2 group to oxaloacetic acid, which is converted into aspartic acid (transamination process): {fOOH C®0 I COOH 'I COOH CH, < : ooh ♦NH, COOH , CHj + ( -H. 1 1 <• ---------- CH-NH, ( '^0 CH — NH іоон ( : ooh COOH + a-Ketoglutaric acid Glutamic acid Oxaloacetic acid IjlOOH CHj R СяО COOH Aspartic acid a-Ketoglutaric acid Third stage. At this stage, urea synthesis is carried out. Citrulline, interacting with the amino group of aspartic acid, forms arginine succinic acid (arginine succinate). In this process, the energy of another ATP molecule isused. NH 2 NH 2 COOH b — O COOH ' C=N — CH NH 2 -CH [ +ATP 7 H L H ’ (СНЛ + ёоон NHj ^OOH CH-NHj * COOH COOH Citrulline Aspartic acid Arginine succinic acid Arginine succinic acid is broken down into arginine and fumaric acid. Fumaric acid is included in carbohydrate metabolism, turning into malic acid, which by dehydrogenation turns into oxalacetic acid. COOH NH, COOH 1 2 NH, C^N-CH г p C-NH NH CH 2 — > NH + (СН 2 ) 3 COOH CH — NH, CH — NH, COOH COOH I H H OOH Arginine succinic acid Arginine Fumaric acid 175