Urea cycle and metabolism of amino groups

The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions that produces urea ((NH2)2CO) from ammonia (NH3). This cycle occurs in ureotelic organisms. The urea cycle converts highly toxic ammonia to urea for excretion. This cycle was the first metabolic cycle to be discovered (Hans Krebs and Kurt Henseleit, 1932), five years before the discovery of the TCA cycle. The urea cycle takes place primarily in the liver and, to a lesser extent, in the kidneys. Amino acid catabolism results in waste ammonia. All animals need a way to excrete this product. Most aquatic organisms, or ammonotelic organisms, excrete ammonia without converting it. Ammonia is toxic, but upon excretion from aquatic species, it is diluted by the water outside the organism. Organisms that cannot easily and safely remove nitrogen as ammonia convert it to a less toxic substance such as urea or uric acid. The urea cycle mainly occurs in the liver. The urea produced by the liver is then released into the bloodstream where it travels to the kidneys and is ultimately excreted in urine. In species including birds and most insects, the ammonia is converted into uric acid or its urate salt, which is excreted in solid form. Source description: [https://en.wikipedia.org/wiki/Urea_cycle Wikipedia] Proteins on this pathway have targeted assays available via the [https://assays.cancer.gov/available_assays?wp_id=WP497 CPTAC Assay Portal].

尿素循环，亦称鸟氨酸循环，是一系列生物化学反应的循环，该循环将氨（NH3）转化为尿素（(NH2)2CO）。此循环存在于尿素排泄型生物体中。尿素循环将剧毒的氨转化为尿素以便排泄。该循环是人类首次发现的代谢循环（汉斯·克雷布斯与库尔特·亨塞尔莱特，1932年），比三羧酸循环的发现早五年。尿素循环主要发生在肝脏，在肾脏中亦有所涉及，但程度较轻。氨基酸分解代谢产生的废物氨。所有动物都需要一种排泄这种产物的方法。大多数水生生物或氨排泄型生物体在未转化氨的情况下直接排泄。氨具有毒性，但一旦从水生生物体中排出，便会被生物体外的水稀释。那些无法轻易且安全地以氨的形式排泄氮的生物体会将其转化为毒性较低的物质，如尿素或尿酸。尿素循环主要发生在肝脏中。肝脏产生的尿素随后释放进入血液循环，并最终随尿液排出体外。在包括鸟类和大多数昆虫在内的物种中，氨被转化为尿酸或其尿酸盐，并以固态形式排出。来源描述：[https://en.wikipedia.org/wiki/Urea_cycle Wikipedia]。该途径上的蛋白质具有通过[https://assays.cancer.gov/available_assays?wp_id=WP497 CPTAC检测门户]可用的针对性检测方法。