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Models of Enzyme Action
酶作用模型
Lock and Key Hypothesis
锁钥学说
This is the simplest model to represent how an enzyme works.
这是表示酶如何工作的最简单的模型。
The substrate simply fits into the active site to form a reaction intermediate just like the key fits in its specific lock.
底物只需放入活性位点即可形成反应中间体，就像钥匙放入其特定的锁中一样。
The shape isn’t changed here, rather the structure of substrate absolutely compliments the structure of the enzyme, like puzzle pieces.
这里的形状没有改变，相反，底物的结构与酶的结构绝对匹配，就像拼图一样。
Induced Fit Hypothesis
诱导契合假说
In this model, the enzyme, upon binding of substrate, changes shape.
在这个模型中，酶与底物结合后会改变形状。
The matching between an enzyme's active site and the substrate isn’t just like two puzzle pieces fitting together, rather the enzyme changes shape and binds to its substrate even more tightly.
酶的活性位点和底物之间的匹配并不像两块拼图拼在一起那样，而是酶改变了形状，并与底物结合得更紧密。
This fine-tuning of the enzyme to “fit” the substrate is called induced fit.
酶的这种微调使其与底物“匹配”，被称为诱导适应。
Environmental Effects on Enzyme Function
环境对酶功能的影响
Active sites are very sensitive.
活性位点非常敏感。
They sense even the slightest change in the environment and respond accordingly.
它们能感觉到环境中哪怕是最轻微的变化，并做出相应的反应。
Some of the factors that affect the active site and consequently enzyme function include:
影响酶活性位点，进而影响酶功能的因素包括:
Temperature
温度
The suitable temperature for enzymes to function properly is 37°C.
酶发挥正常功能的适宜温度为37℃。
Increasing or decreasing the temperature above 37°C affect chemical bonds in the active site, making them less suited to bind substrates.
升高或降低37℃以上的温度会影响活性位点的化学键，使它们不太适合结合底物。
Higher temperatures denature enzymes.
较高的温度会使酶变性。
PH
酸碱度
Amino acids present in the active site are acidic or basic.
活性位点存在的氨基酸是酸性或碱性的。
Fluctuation in pH can affect these amino acids making it hard for substrates to bind.
PH的波动会影响这些氨基酸，使其难以与底物结合。
Extreme pH values can denature enzymes.
极端的pH值会使酶变性。
Enzyme Concentration
酶浓度
Increasing enzyme concentration will increase the rate of reaction, as more enzymes will be available to bind with substrates.
酶浓度增加会加快反应速度，因为有更多的酶可以与底物结合。
However, after a certain concentration, any increase will have no effect on the rate of reaction.
然而，超过一定浓度后，任何增加都不会对反应速度产生影响。
Substrate Concentration
底物浓度
Increasing substrate concentration increases the rate of reaction.
底物浓度越高，反应速度越快。
This is because more substrate molecules will be colliding with enzyme molecules, so more product will be formed.
这是因为更多的底物分子会与酶碰撞，因此会形成更多的产物。
But again, this effect is valid up to a certain concentration.
但同样，这种效应也是在一定浓度下有效。
Inhibition of Enzyme Activity
酶活性抑制
Some evil substances, called “inhibitors”, reduce or even stop the activity of enzymes in biochemical reactions.
一些被称为“抑制物”的有害物质在生化反应中会降低甚至消灭酶的活性。
They either block or distort the active site, thus inhibiting the reaction.
它们要么阻断活性位点，要么扭曲活性位点，从而抑制反应。
Based on this, there are two types of inhibitors given below:
基于此，有以下两种类型的抑制剂:
Competitive Inhibitors:
竞争性抑制剂
Occupy the active site and prevent a substrate molecule from binding to the enzyme.
占据活性位点并阻止底物分子与酶结合。
Non-competitive Inhibitors:
非竞争性抑制剂
Attach to parts of the enzyme, other than the active site, to distort the shape of an enzyme.
附着在酶的活性位点以外的部分上，使酶变形。
