Taylor Zane W, Brown Haley A, Holden Hazel M, Raushel Frank M
Department of Biochemistry & Biophysics, Texas A&M University , College Station, Texas 77843, United States.
Department of Biochemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
Biochemistry. 2017 Nov 21;56(46):6079-6082. doi: 10.1021/acs.biochem.7b00905. Epub 2017 Oct 24.
Campylobacter jejuni is a pathogenic Gram-negative bacterium and a leading cause of food-borne gastroenteritis. C. jejuni produces a capsular polysaccharide (CPS) that contains a unique O-methyl phosphoramidate modification (MeOPN). Recently, the first step in the biosynthetic pathway for the assembly of the MeOPN modification to the CPS was elucidated. It was shown that the enzyme Cj1418 catalyzes the phosphorylation of the amide nitrogen of l-glutamine to form l-glutamine phosphate. In this investigation, the metabolic fate of l-glutamine phosphate was determined. The enzyme Cj1416 catalyzes the displacement of pyrophosphate from MgCTP by l-glutamine phosphate to form CDP-l-glutamine. The enzyme Cj1417 subsequently catalyzes the hydrolysis of CDP-l-glutamine to generate cytidine diphosphoramidate and l-glutamate. The structures of the two novel intermediates, CDP-l-glutamine and cytidine diphosphoramidate, were confirmed by P nuclear magnetic resonance spectroscopy and mass spectrometry. It is proposed that the enzyme Cj1416 be named CTP:phosphoglutamine cytidylyltransferase and that the enzyme Cj1417 be named γ-glutamyl-CDP-amidate hydrolase.
空肠弯曲菌是一种致病性革兰氏阴性菌，是食源性肠胃炎的主要病因。空肠弯曲菌产生一种包含独特的O-甲基磷酰胺修饰（MeOPN）的荚膜多糖（CPS）。最近，阐明了将MeOPN修饰组装到CPS的生物合成途径中的第一步。结果表明，Cj1418酶催化L-谷氨酰胺的酰胺氮磷酸化形成L-谷氨酰胺磷酸。在本研究中，确定了L-谷氨酰胺磷酸的代谢命运。Cj1416酶催化L-谷氨酰胺磷酸取代MgCTP中的焦磷酸形成CDP-L-谷氨酰胺。随后，Cj1417酶催化CDP-L-谷氨酰胺水解生成胞苷二磷酸酰胺和L-谷氨酸。通过磷核磁共振光谱和质谱法确认了两种新型中间体CDP-L-谷氨酰胺和胞苷二磷酸酰胺的结构。建议将Cj1416酶命名为CTP：磷酸谷氨酰胺胞苷酰转移酶，将Cj1417酶命名为γ-谷氨酰-CDP-酰胺水解酶。
