Enzyme thermostability and thermoactivity
Enzyme thermostability and thermoactivity
复制标题
DOI：
10.1093/protein/9.8.629
复制
发表时间：
1996-08-01
期刊：
影响因子：
--
通讯作者：
Pearl, L
中科院分区：
文献类型：
--
作者：
Danson, MJ;Hough, DW;Pearl, L
来自超嗜热微生物（生活在> 85 ℃）的蛋白质是热稳定的，因为它们通常能够承受会使来自嗜温生物（生活在20-40 ℃）如大肠杆菌或人类的大多数蛋白质迅速变性的温度。在大多数情况下，这种稳定性是蛋白质固有的，尽管在一些极端嗜热菌中，这种稳定性在体内通过存在高浓度的细胞内代谢物而增强（Hensel，1993）。因此，来自超嗜热菌的酶具有相当大的生物技术兴趣，因为它们增强的稳定性可以大大降低酶替代成本或允许在高温下进行工艺。随着嗜热菌的发现（Keeling和Doolittle综述，1995），特别是那些可以在超过100 ℃的温度下生长的成员，超嗜热酶学是当前强烈关注和活跃的领域（亚当斯等人，1995）。来自超嗜热菌的酶也是热活性的。几乎所有的最适温度都等于或略高于来源生物的生长温度，这是嗜温生物的最适温度，因此并不意外（索梅罗，1995年）。然而，乍看起来令人惊讶的是，热活性酶在其最适温度下的比活性通常与来自嗜温菌的同源酶在其最适温度下的比活性相当[参见Fdgain（1995）的实例]。也就是说，通常观察到酶反应的温度系数（温度升高10 ℃时反应速率增加的因子）通常为2左右，由此可以预测热活性酶在100 ℃的速率比嗜温菌在37 ℃的速率高60倍以上。因此，有人可能会问：
Proteins from hyperthermophilic micro-organisms (living at> 85 C) are thermostable in that they are usually able to withstand temperatures that would rapidly denature most proteins from mesophiles (living at 20-40 C) such as Escherichia coli or humans. In most cases, the stability is intrinsic to the protein, although in some hyperthermophilic Archaea this stability is augmented in vivo by the presence of high concentrations of intracellular metabolites (Hensel, 1993). Thus, enzymes from hyperthermophiles are of considerable biotechnological interest as their enhanced stability could greatly reduce enzyme replacement costs or permit processes to be carried out at high temperatures. With the discovery of the Archaea (reviewed by Keeling and Doolittle, 1995), and in particular those members that can grow at temperatures in excess of 100 C, hyperthermophilic enzymology is a field of intense current interest and activity (Adams et al, 1995). Enzymes from hyperthermophiles are also thermoactive. Almost all show temperature optima at or slightly above the growth temperature of the source organism, a property shared with those from mesophiles and therefore not unexpected (Somero, 1995). However, what is at first sight surprising is that the specific activity of a thermoactive enzyme at its optimum temperature is often comparable with that of the homologous enzyme from a mesophile at its optimum [see Fdgain (1995) for examples]. That is, it is generally observed that the temperature coefficients (the factor by which the rate of a reaction is increased on raising the temperature by 10 C) are usually around 2 for enzymic reactions, and from this one would predict a more than a 60-fold higher rate for the thermoactive enzyme at 100 C than that of the mesophile at 37 C. One might therefore ask: