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If you want to improve natural enzyme performance, there are approaches that work in almost every case.
如果你想提高天然酶的性能，也有一些几乎在所有情况下都奏效的方法。
Chemical reactions tend to work better at higher temperatures, for instance (this is why, if you want to make a cake, it is better to set the oven at 180C rather than 50C); but most enzymes are most stable at the ambient temperature of the organism they work in – 37C in the case of humans.
例如，化学反应往往在较高温度下效果更好(这就是为什么如果想做蛋糕，最好把烤箱温度调到180摄氏度，而不是50摄氏度)；但大多数酶在它们所作用的生物体的环境温度下最稳定，比如37摄氏度的人体体温。
By rewriting the DNA that codes an enzyme, scientists can tweak its structure and function, making it more stable at higher temperatures, say, which helps it work faster.
通过重写编码酶的DNA，科学家就可以调整其结构和功能，例如，使其在更高温度下更稳定，这将有助于酶更快地起作用。
This power sounds godlike, but there are many limitations.
这种能力听起来神乎其神，但却存在很多限制。
“It is often two steps forward, one step back,” says Elizabeth Bell, a researcher at the US government’s National Renewable Energy Laboratory (NREL) in Colorado.
美国科罗拉多州的国家可再生能源实验室(NREL)的研究员伊丽莎白·贝尔说：“这通常是前进两步，倒退一步。”
Evolution itself involves tradeoffs, and while scientists understand how most enzymes work, it remains difficult to predict the tweaks that will make them work better.
进化本身就涉及权衡，虽然科学家了解大多数酶的工作原理，但仍然很难预测哪些调整将会使其工作得更好。
“Logical design tends not to work very well, so we have to take other approaches,” says Bell.
“逻辑设计往往效果不佳，所以我们必须采取其他方法，”贝尔说。
Bell’s own work – which focuses on PETase, the enzyme that Ideonella sakaiensis produces to break down PET plastics – takes a brute-force approach in order to turbocharge natural evolution.
贝尔的研究主要集中在大阪堺菌产生的用于分解PET塑料的酶上。为加速自然进化，贝尔采用了穷举法。
Bell takes the regions of the enzyme that work directly on plastic and uses genetic engineering to subject them to every possible mutation.
贝尔提取了直接作用于塑料的酶区域，并利用基因工程使其进行各种可能的突变。
In the wild, a mutation in an enzyme might occur only once in every few thousand times the bacteria divide.
在野外，每当细菌分裂几千次，一种酶就发生一次突变。
Bell ensures she gets hundreds, or thousands of potentially beneficial mutants to test.
贝尔确保自己能够获得数百上千个潜在有益的突变体来进行测试。
She then measures each one for its ability to degrade plastic.
接着，她对每个突变体的降解塑料能力进行测量。
Any candidates that show even marginal improvement get another round of mutations.
任何显示出哪怕是微小改进的候选物质都会再进行一轮突变。
The head of the NREL research group, Gregg Beckham, refers to it as “evolving the crap out of an enzyme”.
国家可再生能源实验室研究小组的负责人格雷格·贝克汉姆将其称为“对酶进行彻底进化”。
Last year, she published her latest findings, on a PETase enzyme she had engineered that could degrade PET many times faster than the original enzyme.
去年，贝尔发表了她设计的一种PET酶的最新发现，这种酶比原始酶降解PET的速度快了好多倍。
