Studies on the Formation of Dimethylamine and its Metabolic Fate in Higher Animals

从大鼠肾脏中纯化出一种参与N^G， N^G-二甲基精氨酸（DMA）代谢的新酶N^G， N^G-二甲基精氨酸二甲氨基水解酶。该酶由一个多肽组成，其分子量约为33,000。酶的pI是pH 5.2。该酶催化DMA的二甲基氨基部分水解释放，形成l-环氨酸和二甲胺。它对DMA和N^ g -单甲基- l-精氨酸（MMA）具有高度特异性，这两种氨基酸的Km值分别为0.18和0.36 mM。该酶在pH为6.5时活性最大，且不需要辅助因子。sh -阻断剂和二价金属离子强烈抑制其活性。从BALB/c小鼠制备了针对纯化酶的单克隆抗体，并用于酶的分布分析。在雄性和雌性大鼠的各种组织中都发现了该酶的活性和蛋白质，表明在体液中释放的DMA和MMA很容易被该酶水解，形成l -瓜氨酸和二甲胺或一甲基胺。二甲胺在各种组织中被同位素释放，大约90%的二甲胺被释放出来，没有进一步的降解，很容易在尿液中排出。微量二甲胺被代谢为尿素和未识别的酸性或中性化合物。目前尚不清楚微量代谢物是否含有亚硝基二甲胺。本实验结果表明，该酶能分解代谢内皮衍生放松因子（EDRF）、DMA和MMA的阻滞剂。这一事实可能促使人们进一步研究该酶的作用与内皮细胞产生edrf的调节之间的关系。

A new enzyme, N^G, N^G-dimethylarginine dimethylaminohydrolase which plays a role in the metabolism of N^G, N^G-dimethyl-L-arginine (DMA), has been purified to homogeneity from rat kidney. The enzyme consists of a single polypeptide and its molecular weight is about 33,000. The pI of the enzyme is at pH 5.2. The enzyme catalyzes the hydrolytic liberation of the dimethyl-amino moiety of DMA and forms L-cirulline and dimethylamine. It is highly specific for DMA and N^G-monomethyl-L-arginine (MMA), and Km values for these amino acids are 0.18 and 0.36 mM, respectively. The enzyme shows the maximum activity at pH 6.5 and requires on co-factor. The activity is strongly inhibited by SH-blocking reagents and divalent metal ions. The monoclonal antibody against the purified enzyme was prepared from the BALB/c mouse and used for the analyze of the distribution of the enzyme. Both the enzyme activity and protein were found in various tissues of male and female rats, suggesting that DMA and MMA liberated in body fluids may readily hydrolyzed by this enzyme to form L-citrulline and dimethylamine or monomethylamine. The liberation of dimethylamine from DMA in various tissues was demonstrated isotopically and about 90% of the dimethylamine liberated was readily excreted in urne without further degradation. Trace amounts of dimethylamine were metabolized to urea and unidentified acidic or neutral compounds. It remains still unclear whether the trace metabolites containnitrosodimethylamine. The results of this experiment shows that the enzyme catabolizes the blockers of Endotherium-Derived Relaxing Factor (EDRF), DMA and MMA. This fact may prompt the further investigation on the relationship between the role of this enzyme and the regulation of EDRF-production from endotherial cells.