Enzymes and Their Role in Living Organisms | 酶及其在生物体中的作用

📚 Enzymes and Their Role in Living Organisms | 酶及其在生物体中的作用

Enzymes are biological catalysts that speed up chemical reactions in living cells without being used up in the process. They are essential for almost every metabolic reaction, from digestion to DNA replication. In this article, we will explore the structure, function, and importance of enzymes, as well as the factors that affect their activity.

酶是生物催化剂，能在不自身消耗的情况下加速活细胞中的化学反应。从消化到DNA复制，几乎每一个代谢反应都离不开酶。在本文中，我们将探讨酶的结构、功能和重要性，以及影响酶活性的因素。

1. What Are Enzymes? | 什么是酶？

Enzymes are proteins made of long chains of amino acids folded into specific three-dimensional shapes. Each enzyme has an active site, a unique region where the substrate (the reactant) binds. The shape of the active site is complementary to the substrate, enabling a high degree of specificity.

酶是由氨基酸长链折叠成特定三维形状的蛋白质。每种酶都有一个活性位点，这是底物（反应物）结合的特殊区域。活性位点的形状与底物互补，从而具有高度特异性。

Enzymes are not changed by the reaction; they can be reused.

酶在反应中不被改变，可以重复使用。
They lower the activation energy required for a reaction.

它们降低反应所需的活化能。
Enzymes work best under specific conditions called optimum conditions.

酶在称为最适条件的特定条件下工作效果最佳。

2. How Enzymes Work: The Lock and Key Model | 酶如何工作：锁钥模型

The classic model for enzyme action is the lock and key model. The enzyme is the lock, and the substrate is the key. Only the correct substrate fits perfectly into the active site, just as only the correct key opens a lock.

酶作用的经典模型是锁钥模型。酶是锁，底物是钥匙。只有正确的底物才能完美地嵌入活性位点，就像只有正确的钥匙才能打开锁一样。

Enzyme + Substrate → Enzyme–Substrate Complex → Enzyme + Product

酶 + 底物 → 酶-底物复合物 → 酶 + 产物

In reality, the active site is flexible and slightly changes shape to fit the substrate. This is called the induced fit model. Both models emphasise the complementary relationship between enzyme and substrate.

实际上，活性位点具有一定的灵活性，会稍微改变形状以适应底物。这被称为诱导契合模型。两种模型都强调酶与底物之间的互补关系。

3. Temperature and Enzyme Activity | 温度与酶活性

Temperature affects the kinetic energy of molecules. As temperature increases, molecules move faster, leading to more frequent collisions between enzymes and substrates, so the rate of reaction increases. However, beyond the optimum temperature, the enzyme begins to denature.

温度影响分子的动能。随着温度升高，分子运动加快，酶与底物碰撞更频繁，反应速率增加。然而，超过最适温度后，酶开始变性。

Optimum temperature for most human enzymes is about 37 °C.

大多数人体酶的最适温度约为37 °C。
At high temperatures, bonds in the protein break, changing the shape of the active site.

高温下，蛋白质中的化学键断裂，活性位点的形状发生改变。
Denaturation is permanent and irreversible.

变性是永久且不可逆的。

4. pH and Enzyme Activity | pH与酶活性

Each enzyme has an optimum pH. Changes in pH alter the concentration of hydrogen ions, which can disrupt ionic bonds and hydrogen bonds within the enzyme. This changes the shape of the active site and reduces enzyme activity.

每种酶都有最适pH。pH的变化会改变氢离子浓度，从而破坏酶内的离子键和氢键，改变活性位点的形状，降低酶活性。

Enzyme	Optimum pH
Pepsin (stomach)	2.0
Amylase (saliva)	7.0
Trypsin (small intestine)	8.0

Extreme pH values cause denaturation, just like high temperature.

极端pH值同样会导致酶变性，与高温类似。

5. Enzyme and Substrate Concentration | 酶浓度与底物浓度

The rate of an enzyme-catalysed reaction depends on how often enzymes and substrates collide. Increasing enzyme concentration increases the number of active sites, so the rate rises until the substrate is exhausted.

酶催化反应的速率取决于酶与底物碰撞的频率。增加酶浓度会增加活性位点的数量，因此反应速率上升，直到底物被耗尽。

As substrate concentration increases, the rate initially rises.

随着底物浓度增加，反应速率起初上升。
At saturation, all active sites are occupied, so the rate plateaus.

当饱和时，所有活性位点都被占用，反应速率趋于平稳。
Adding more enzyme at saturation will increase the rate again.

在饱和状态下再加入酶，反应速率会再次升高。

6. Inhibitors | 抑制剂

Inhibitors are substances that reduce enzyme activity. They can be competitive, directly blocking the active site, or non-competitive, binding elsewhere and altering the enzyme shape.

抑制剂是降低酶活性的物质。它们可以是竞争性的，直接占据活性位点；也可以是非竞争性的，与其他部位结合并改变酶的形状。

Type	Effect
Competitive	Competes with substrate for the active site; can be overcome by high substrate concentration.
Non-competitive	Binds to another site; changes active site shape; cannot be overcome by substrate.

Competitive inhibitors are often used as drugs. For example, some HIV drugs competitively inhibit viral enzymes.

竞争性抑制剂常被用作药物。例如，一些抗HIV药物可竞争性抑制病毒酶。

7. Enzymes in Digestion | 消化中的酶

Digestive enzymes break down large food molecules into smaller soluble molecules that can be absorbed. They are produced by glands and the lining of the digestive tract.

消化酶将大分子食物分解成可被吸收的小分子可溶性物质。它们由腺体和消化道内壁分泌。

Amylase breaks starch into maltose.

淀粉酶将淀粉分解为麦芽糖。
Proteases (e.g. pepsin) break proteins into amino acids.

蛋白酶（如胃蛋白酶）将蛋白质分解为氨基酸。
Lipase breaks lipids into fatty acids and glycerol.

脂肪酶将脂质分解为脂肪酸和甘油。

These enzymes work at different pH conditions, which is why the digestive system has specialised regions.

这些酶在不同pH条件下工作，这就是消化系统拥有特化区域的原因。

8. Industrial Applications of Enzymes | 酶的工业应用

Enzymes are widely used in industry because they are specific, efficient, and environmentally friendly. Biological washing powders contain enzymes like proteases and lipases to remove stains.

酶因其特异性、高效性和环保性而被广泛应用于工业。生物洗衣粉含有蛋白酶和脂肪酶，可去除污渍。

Proteases in washing powder break down protein stains.

洗衣粉中的蛋白酶分解蛋白质污渍。
Carbohydrases convert starch into sugar syrup.

糖化酶将淀粉转化为糖浆。
Immobilised enzymes are used in biosensors to measure glucose levels.

固定化酶被用于生物传感器中测量血糖水平。

Using enzymes reduces the need for high temperatures and harsh chemicals, saving energy and reducing pollution.

使用酶可减少高温和强化学试剂的需求，从而节省能源并减少污染。

9. Summary | 总结

Enzymes are vital biological catalysts with specific active sites that allow them to speed up reactions efficiently. Their activity is affected by temperature, pH, and concentrations of enzyme and substrate. Understanding enzymes is essential for medicine, industry, and biology.

酶是重要的生物催化剂，其特定活性位点使其能够高效加速反应。它们的活性受温度、pH、酶和底物浓度的影响。理解酶对医学、工业和生物学都至关重要。

Enzymes: Specific, Reusable, and Regulated | 酶：特异性、可重复使用且受调控

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Enzymes and Their Role in Living Organisms | 酶及其在生物体中的作用