Purification and some properties of citrate synthase from a nitrite-oxidizing chemoautotroph,Nitrobacter agilis ATCC 14123 |
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| Affiliation: | 1. Department of Neuroscience, Karolinska Institutet, SE-171 77, Stockholm, Sweden;2. Department of Medicine, Karolinska Institutet, SE-171 76, Stockholm, Sweden;1. Department of Food and Biotechnology, Korea University, Sejong, Republic of Korea;2. School of Life Sciences and Biotechnology, BK21 Plus KNU Creative BioResearch Group, College of Natural Sciences, Kyungpook National University, Taegu, Republic of Korea;1. Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China;2. Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China;3. Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi 214122, China;4. National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, Wuxi 214122, China |
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| Abstract: | ![]()
Citrate (si)-synthase (citrate oxaloacetate-lyase, EC 4.1.3.7) was purified as an electrophoretically homogeneous protein from a nitrite-oxidizing chemoautotrophic bacterium, Nitrobacter agilis ATCC 14123. The molecular mass (Mr) of the native enzyme was estimated to be about 250,000 by gel filtration, whereas SDS-PAGE gave two bands with Mr values of 45,000 and 80,000, respectively, suggesting that the enzyme is a tetramer consisting of two different subunits (α: 45,000, β: 80,000). The isoelectric point of the enzyme was 5.4. The pH and temperature optima on the citrate synthase activity were about 7.5–8.0 and 30–35°C, respectively. The citrate synthase was stable in the pH range of 6.0–9.0 and up to 55°C. The apparent Km values for oxaloacetate and acetyl-CoA were about 27 μM and 410 μM, respectively. The activity of citrate synthase was not inhibited by ATP (1 mM), NADH (1 mM) or 2-oxoglutarate (10 mM), but was strongly inhibited by SDS (1 mM). Activation by metal ions was not observed. |
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