enzyme(enzyme)
在活性生物体中起催化剂作用的物质，它调节化学反应中的反应速率（reaction rate）而自身不被改变。它减低了开始这些反应所需的活化能（activation energy）；少了它，多数都无法在有用效的速率中发生。在它们参与的催化反应中并不会消耗掉，可以被反覆利用，催化一个反应只需要很小的数量。催化细胞新陈代谢的各个方面，包括大营养素分子（如蛋白质、碳水化合物和脂肪）被断裂成较小分子的食物消化过程、化学能的守恒和转变，以及从较小的前体构成细胞大分子。几乎所有的都是蛋白质。有许多包含了一个辅助因子（cofactor），它可能是有机化合物（如维生素），或是无机金属离子（如铁、锌）。它的辅助因子结合了活性构型（configuration），通常包括引起适切反应的活性物质。的活性可以通过多种途径抑制。当与基质分子十分相似的分子与的活性部位相结合并阻碍与实际基质的结合时，就会发生竞争抑制。如果的构型被改变（参阅denaturation），那麽它就会失去其活性。依其反应的形式可分成︰一、氧化还原反应；二、转移；三、水解（hydrolysis）；四、裂解；五、异构（isomerization，参阅isomer、isomerism）；六、连接或合成（聚合）。一种仅与一类或一组被称为基质的物质相互作用催化某一种反应，由於这一特点，常常在基质名称後加上「-ase」来命名。工业上利用来发酵（fermentation）葡萄酒、面包，凝结乳酪和酿造啤酒，它在医药上的用途有杀死致病微生物、促进伤口癒合及诊断某些疾病。
English version：
enzyme
Substance that acts as a catalyst in living organisms, regulating the reaction rate at which life's chemical reactions proceed without being altered in the process. Enzymes reduce the activation energy needed to start these reactions; without them, most would not take place at a useful rate. Because they are not consumed, only tiny amounts are needed. Enzymes catalyze all aspects of cell metabolism; including the digestion of food, in which large nutrient molecules (including proteins, carbohydrates, and fats) are broken down into smaller molecules, the conservation and transformation of chemical energy, and the construction of cellular materials and components. Almost all enzymes are proteins; many contain a cofactor, either an organic compound (e.g., a vitamin) or an inorganic ion (e.g., iron, zinc). The enzyme-cofactor combination assumes an active configuration, usually including an active site for the substance (substrate) involved in the reaction to fit into. Many enzymes are specific to one substrate. If a competing molecule blocks the active site or changes its shape, the enzyme's activity is inhibited. If the configuration is destroyed (see denaturation), its activity is lost. Enzymes are classified by the type of reaction they catalyze: (1) oxidation-reduction; (2) transfer of a chemical group; (3) hydrolysis; (4) removal or addition of a chemical group; (5) isomerization (see isomer, isomerism); and (6) binding together of substrate units (polymerization). Most enzyme names end in “-ase.” Enzymes are chiral catalysts, producing mostly or only one of the possible stereoisomeric products (see optical activity). Fermentation of wine, leavening of bread, curdling of milk into cheese, and brewing of beer all are enzymatic reactions. Uses in medicine include killing disease-causing microorganisms, promoting wound healing, and diagnosing certain diseases.