Two enzymes which degrade urea have been described, urease and ATP-urea amidolyase
Both enzymes catalyse the degradation of urea to NH3 and CO2.
There are five key enzymes in the urea cycle: carbamoyl-phosphate synthetase 1 (CPS1),
ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS1),
argininosuccinate lyase (ASL), and arginase 1 (ARG1).
Additionally, a sixth enzyme, N-acetylglutamate synthase (NAGS),
is critical for urea cycle function, providing CPS1 with its necessary cofactor.
尿素循環中有五種關鍵酶:氨甲醯磷酸合成酶1(CPS1),鳥氨酸轉氨甲醯酶(OTC),
精氨琥珀酸合成酶(ASS1),精氨琥珀酸裂合酶(ASL)和精氨酸酶1(ARG1)。
此外,第六種酶N-乙醯谷氨酸合酶(NAGS)對尿素循環功能至關重要,為CPS1提供了必需的輔因子。
Deficiencies in any of these enzymes result in elevated blood ammonia concentrations,
which can have detrimental effects, including central nervous system dysfunction,
brain damage, coma, and death.
任何這些酶的缺陷導致血氨濃度升高,其可能具有不利影響,包括中樞神經系統功能障礙,腦損傷,昏迷和死亡。
One interpretation of these results is that urea degradation is a Mn-, Zn-,
or Fe-dependent process that is inhibited by calprotectin.
對這些結果的一種解釋是尿素降解是Mn(錳),Zn(鋅)或Fe(鐵)依賴性過程。
On the other hand the hepatic activity of the mitochondrial
localized glutamate dehydrogenase of the zinc-deficient rats was significantly increased
and the carbamoylphosphate synthetase and ornithine carbamoyltransferase
were reduced about half in comparison with both control groups.
缺鋅,氨基甲醯磷酸合成酶(CPS)和鳥氨酸氨甲醯基轉移酶與對照組相比減少約一半。
Cirrhotic rats which received zinc supplementation showed an increase in liver OTC activity
,positively correlated with serum and hepatic zinc content.
接受鋅補充劑,肝的鳥氨酸轉氨甲醯酶活性(OTC)增加,與血清和肝的鋅含量呈正相關。
精胺酸是一種親水性鹼性胺基酸,由瓜胺酸透個胞質酵素精氨基琥珀酸合酶(ASS)
及精氨基琥珀酸裂解酶(ASL)合成
精氨琥珀酸合成酶(ASS)需鎂離子
In neurons, arginase is a central urea cycle enzyme,
and the metal manganese (Mn) is an essential cofactor.
在神經元中,精氨酸酶是一種中心的尿素循環酶,而金屬錳(Mn)是一種重要的輔助因子。
精氨酸酶,是一種含錳的酶。
催化反應:L-精氨酸+H2O⇔L-鳥氨酸+尿素
N-Acetyl-L-glutamate synthetase catalyzes the synthesis of N-acetyl-L-glutamate,
an allosteric and essential activator of carbamoyl-phosphate synthetase I
in the liver of ureotelic animals.
N-乙醯-L-谷氨酸合成酶(NAGS)催化N-乙醯-L-谷氨酸的合成,
尿毒症動物肝臟中氨基甲醯磷酸合成酶I的變構和必需激活劑。
The enzyme is activated specifically by arginine.
該酶特別被精氨酸激活。
高血氨症--尿素循環代謝異常
精胺酸促進體內尿素生成而降低血氨
易達康L-精胺酸
瓜胺酸去除會損害活細胞的氨毒。瓜氨酸在體內將代謝成精氨酸。
瓜氨酸含量高的食物
天門冬胺酸有助於血液中的氨轉變為尿素排出體外,消除過多的阿摩尼亞
含天冬胺酸的食物:雞蛋、牛奶或起司、杏仁、核桃、葵花子、芝麻、南瓜
紅茶:天冬氨酸2032(每100克中含毫克)
小結3:
因為
將毒性較強的氨,轉為較為無害的尿素或尿酸
轉換NH3(氨)跟CPS1有關
又NAGS為CPS1提供了必需的輔因子
所以
將毒性較強的氨,轉為較為無害的尿素應該最主要跟鋅、精氨酸有關
而