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Designer enzymes enjoy life in the hot seat

点击量:   时间:2017-07-16 01:01:09

By Charles Seife MOST enzymes that survive at high temperatures trade efficiency for heat-resistance. But a spot of genetic tinkering by scientists has produced an enzyme that is twenty times more active when things get really hot than any enzyme that occurs in nature. High-temperature industrial processes could reap the benefits. The new enzyme is quite happy at 100 °C—and beyond. Some “extremophilic” bacteria do thrive in temperatures close to boiling point—around hydrothermal vents on the ocean floor, for instance. But the cost of living dangerously is high: their enzymes, reinforced to stop them falling apart in the heat, are relatively inflexible and do not work efficiently. The most temperature-stable proteins, which can stay together even in boiling water, are the least efficient. A team led by Bertus Van den Burg of the University of Groningen in the Netherlands hoped to improve the heat tolerance of a protein-splitting enzyme made by the hot-spring bacterium Bacillus stearothermophilus. The enzyme usually breaks down at 80 °C. The team introduced eight mutations, some of which put bulkier amino acids into the sequence, making them less likely to fly around. Others created a disulphide bridge, cementing a hairpin turn in the enzyme’s structure. With these mutations, the enzyme survived well at 100 °C, and did not break down until temperatures reached about 110 °C. And since the mutations were distant from the end of the enzyme that splits proteins, it did not lose any of its ability to do its job. In the current issue of Proceedings of the National Academy of Sciences (vol 95, p 2056), the researchers say that their designer enzyme is twenty times more active than natural extremophilic enzymes. “The most exciting thing is that not only were we able to stabilise the enzyme by almost 30 °C, we maintained its activity,