Jones M V, Spencer W N
Antonie Van Leeuwenhoek. 1985;51(2):193-201. doi: 10.1007/BF02310012.
The thermostability of four enzymes of the tricarboxylic acid cycle has been studied in the facultative thermophile, Bacillus coagulans. Although isocitrate dehydrogenase appeared to be more temperature-sensitive in whole-cell extracts of cultures grown at 30 degrees C compared with that in cultures grown at 55 degrees C, this difference could be largely eliminated by the removal of cell-wall material. The specific activity of each of the enzymes examined was approximately threefold higher in cultures grown at 55 degrees C than in those grown at 30 degrees C. The maximum temperature, Arrhenius plot and effect of stabilizing agents for each enzyme were examined and found to be independent of growth temperature. Sodium chloride (10% w/v) was an effective protective agent for fumarase, aconitase and malate dehydrogenase. Protection from thermal denaturation of isocitrate dehydrogenase, aconitase and fumarase but not malate dehydrogenase was also given when the enzymes were heated in the presence of their substrates. These results are discussed in light of the generalized theories of facultative thermophily which have been proposed.
已在兼性嗜热菌凝结芽孢杆菌中研究了三羧酸循环中四种酶的热稳定性。尽管与在55℃培养的培养物相比，异柠檬酸脱氢酶在30℃培养的培养物的全细胞提取物中似乎对温度更敏感，但通过去除细胞壁物质，这种差异可在很大程度上消除。在55℃培养的培养物中，所检测的每种酶的比活性比在30℃培养的培养物中大约高三倍。研究了每种酶的最高温度、阿伦尼乌斯曲线和稳定剂的作用，发现它们与生长温度无关。氯化钠（10% w/v）是延胡索酸酶、乌头酸酶和苹果酸脱氢酶的有效保护剂。当酶在其底物存在下加热时，异柠檬酸脱氢酶、乌头酸酶和延胡索酸酶但不是苹果酸脱氢酶也受到热变性保护。根据已提出的兼性嗜热性的一般理论对这些结果进行了讨论。
