{"title":"Mechanism of arginine biosynthesis in Chlamydomonas reinhardti I. Purification and properties of ornithine acetyltransferase","authors":"Maria Staub, G. Dénes","doi":"10.1016/0926-6593(66)90144-5","DOIUrl":null,"url":null,"abstract":"<div><p></p><ul><li><span>1.</span><span><p>1. Ornithine acetyltransferase (proposed name, <span><math><mtext>α-N-</mtext><mtext>acetyl-</mtext><mtext>l</mtext><mtext>-ornithine:</mtext><mtext>l</mtext><mtext>-glutamate</mtext></math></span><em>N</em>-acetyltransferase) which catalyzes the first step in arginine biosynthesis, the formation of <em>N</em>-acetylglutamate from <span><math><mtext>α-N-</mtext><mtext>acetyl-</mtext><mtext>l</mtext><mtext>-ornithine</mtext></math></span> and <span>l-glutamate</span>, has been isolated from the freshwater alga <em>Chlamydomonas reinhardti</em>.</p></span></li><li><span>2.</span><span><p>2. The enzyme has a broad pH optimum between 7.5 and 9. The <em>K</em><sub><em>m</em></sub> value of the enzyme at pH 7.5 is 1.3 · 10<sup>−2</sup> M for glutamate and 5.5 · 10 <sup>−3</sup> M for <span><math><mtext>α-N-</mtext><mtext>acetyl-</mtext><mtext>l</mtext><mtext>-ornithine</mtext></math></span>. The reaction is reversible; the equilibrium constant expressed as <em>K</em> = [acetylglutamate][ornithine]/[acetylornithine][glutamate] is 0.47.</p></span></li><li><span>3.</span><span><p>3. Beside the transferase activity, the enzyme has also a hydrolytic activity. The rate of the hydrolytic reaction for <em>α</em>-<em>N</em> acetylornithine is 1% of that of the acetyltransferase reaction.</p></span></li><li><span>4.</span><span><p>4. No specific cofactor has been found. The enzyme is inhibited by <em>p</em>-chloromercuribenzoate, but not by iodoacetate.</p></span></li></ul></div>","PeriodicalId":100160,"journal":{"name":"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation","volume":"128 1","pages":"Pages 82-91"},"PeriodicalIF":0.0000,"publicationDate":"1966-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0926-6593(66)90144-5","citationCount":"34","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Biochimica et Biophysica Acta (BBA) - Enzymology and Biological Oxidation","FirstCategoryId":"1085","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0926659366901445","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 34
Abstract
1.
1. Ornithine acetyltransferase (proposed name, N-acetyltransferase) which catalyzes the first step in arginine biosynthesis, the formation of N-acetylglutamate from and l-glutamate, has been isolated from the freshwater alga Chlamydomonas reinhardti.
2.
2. The enzyme has a broad pH optimum between 7.5 and 9. The Km value of the enzyme at pH 7.5 is 1.3 · 10−2 M for glutamate and 5.5 · 10 −3 M for . The reaction is reversible; the equilibrium constant expressed as K = [acetylglutamate][ornithine]/[acetylornithine][glutamate] is 0.47.
3.
3. Beside the transferase activity, the enzyme has also a hydrolytic activity. The rate of the hydrolytic reaction for α-N acetylornithine is 1% of that of the acetyltransferase reaction.
4.
4. No specific cofactor has been found. The enzyme is inhibited by p-chloromercuribenzoate, but not by iodoacetate.
1.1. 从莱茵衣藻(Chlamydomonas reinhardti)中分离到一种鸟氨酸乙酰转移酶(拟命名为α- n -乙酰基-l-鸟氨酸:l-谷氨酸乙酰转移酶),它催化精氨酸生物合成的第一步,即α- n -乙酰基-l-鸟氨酸和l-谷氨酸形成n -乙酰谷氨酸。这种酶的最适pH值在7.5到9之间。在pH 7.5时,谷氨酸酶的Km值为1.3·10−2 M, α- n -乙酰-l-鸟氨酸酶的Km值为5.5·10−3 M。反应是可逆的;用K =[乙酰谷氨酸][鸟氨酸]/[乙酰鸟氨酸][谷氨酸]表示的平衡常数为0.47.3.3。除了转移酶活性外,该酶还具有水解活性。α-N乙酰鸟氨酸水解反应速率为乙酰转移酶反应速率的1%。没有发现具体的辅助因子。对氯脲苯甲酸酯对该酶有抑制作用,而碘乙酸对其无抑制作用。