Nawaz M S, Zhang D, Khan A A, Cerniglia C E
Division of Microbiology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Appl Microbiol Biotechnol. 1998 Nov;50(5):568-72. doi: 10.1007/s002530051336.
A gram-negative, rod-shaped bacterium capable of utilizing L-asparagine as its sole source of carbon and nitrogen was isolated from soil and identified as Enterobacter cloacae. An intracellularly expressed L-asparaginase was detected and it deaminated L-asparagine to aspartic acid and ammonia. High-pressure liquid chromatography analysis of a cell-free asparaginase reaction mixture indicated that 2.8 mM L-asparagine was hydrolyzed to 2.2 and 2.8 mM aspartic acid and ammonia, respectively, within 20 min of incubation. High asparaginase activity was found in cells cultured on L-fructose, D-galactose, saccharose, or maltose, and in cells cultured on L-asparagine as the sole nitrogen source. The pH and temperature optimum of L-asparaginase was 8.5 and 37-42 degrees C, respectively. The half-life of the enzyme at 30 degrees C and 37 degrees C was 10 and 8 h, respectively.
从土壤中分离出一种革兰氏阴性、杆状细菌，它能够利用L-天冬酰胺作为唯一的碳源和氮源，并被鉴定为阴沟肠杆菌。检测到一种细胞内表达的L-天冬酰胺酶，它将L-天冬酰胺脱氨生成天冬氨酸和氨。对无细胞天冬酰胺酶反应混合物进行高压液相色谱分析表明，在孵育20分钟内，2.8 mM的L-天冬酰胺分别水解为2.2 mM和2.8 mM的天冬氨酸和氨。在以L-果糖、D-半乳糖、蔗糖或麦芽糖培养的细胞中，以及在以L-天冬酰胺作为唯一氮源培养的细胞中，发现了高天冬酰胺酶活性。L-天冬酰胺酶的最适pH和温度分别为8.5和37 - 42℃。该酶在30℃和37℃下的半衰期分别为10小时和8小时。
