Isolation and characterization of salt-tolerant glutaminases from marine Micrococcus luteus K-3 |
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| Institution: | 1. Laboratory of Enzyme Technology, Department of Biotechnology, School of Food, Biotechnology and Development, Agricultural University of Athens, 75 Iera Odos Street, GR-11855-Athens, Greece;2. Department of Pharmacognosy, College of Pharmacy, Prince Sattam Bin Abdulaziz University, 11942 Alkharj, Saudi Arabia;3. Department of Microbiology, College of Science, Al-Azhar University, Nasr City, 11884, Cairo, Egypt;1. Center for Endocrinology, Diabetes & Metabolism, Children''s Hospital Los Angeles, Los Angeles, CA, United States;2. Department of Molecular Medicine, Unit of Immunology and General Pathology, University of Pavia, Italy;3. Center for Childhood Cancer and Blood Diseases, Children''s Hospital Los Angeles, Los Angeles, CA, United States;4. Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States;5. Department of Physiology & Biophysics, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States;1. State Key Laboratory of Food Science and Technology, Ministry of Education, Key Laboratory of Carbohydrate Chemistry and Biotechnology, Jiangnan University, Wuxi, Jiangsu 214122, People''s Republic of China;2. Taiji Group Zhejiang Dongfang Pharmaceutical Co. Ltd., Shaoxing, Zhejiang 312000, People''s Republic of China;3. Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi 214122, People''s Republic of China |
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| Abstract: | Marine Micrococcus luteus K-3 constitutively produced two salt-tolerant glutaminases, designated glutaminase I and II. Glutaminase I was homogeneously purified about approximately, 1620-fold with a 4% yield, and was a dimer with a molecular weight of about 86,000. Glutaminase II was partially purified about 190-fold with a 0.04% yield. The molecular weight of glutaminase II was also 86,000. Maximum activity of glutaminase I was observed at pH 8.0, 50°C and 8–16% NaCl. The optimal pH and temperature of glutaminase II were 8.5 and 50°C. The activity of glutaminase II was not affected by the presence of 8 to 16% NaCl. The presence of 10% NaCl enhanced thermal stability of glutaminase I. Both enzymes catalyzed the hydrolysis of l-glutamine, but not its hydroxylaminolysis. The Km values for l-glutamine were 4.4 (glutaminase I) and 6.5 mM (glutaminase II). Neither of the glutaminases were activated by the addition of 2 mM phosphate or 2 mM sulfate. p-Chloromercuribenzoate (0.01 mM) significantly inhibited glutaminase I, but not glutaminase II. The conserved sequences LA**V and V**GGT*A were observed in the N-terminal amino acid sequences of glutaminase I, similar to that for other glutaminases. |
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