酶Enzyme

底物结合在酶的活性中心形成酶-底物复合物，酶通过稳定过渡态降低活化能。具体机制包括：邻近与定向效应、酸碱催化、共价催化（如丝氨酸蛋白酶的酰基-酶中间体）、金属离子催化和底物形变。费歇尔在 1894 年提出“锁钥学说”，1958 年科什兰提出“诱导契合学说”，认为底物结合会引起酶构象变化。动力学上服从米氏方程 v = V_max[S]/(K_m + [S])。

The substrate binds the active site to form an enzyme–substrate complex, and the enzyme lowers the activation energy by stabilising the transition state. Mechanisms include proximity and orientation effects, acid–base catalysis, covalent catalysis (as in the acyl-enzyme of serine proteases), metal-ion catalysis and substrate strain. Fischer proposed the lock-and-key model in 1894, and Koshland the induced-fit model in 1958, in which binding changes the enzyme's shape. Kinetics follow the Michaelis–Menten equation, v = V_max[S]/(K_m + [S]).

1833 年佩扬和佩索兹从麦芽中分离出淀粉酶。1878 年屈内创造 enzyme 一词（希腊语“在酵母中”）。1897 年布赫纳证明无细胞提取液能发酵。1913 年米凯利斯和门滕建立酶动力学方程。1926 年萨姆纳结晶出脲酶，1930 年代诺思罗普结晶出胃蛋白酶等，证明酶是蛋白质，二人获 1946 年诺贝尔化学奖。1965 年菲利普斯解析溶菌酶结构，是第一个解析的酶结构。

In 1833 Payen and Persoz isolated amylase (diastase) from malt. Kühne coined the word enzyme, Greek for 'in yeast', in 1878. Buchner showed in 1897 that cell-free extracts ferment sugar. Michaelis and Menten derived their rate equation in 1913. Sumner crystallised urease in 1926 and Northrop crystallised pepsin and others in the 1930s, proving enzymes are proteins; they shared the 1946 Nobel Prize in Chemistry. In 1965 Phillips solved the structure of lysozyme, the first enzyme structure.

国际酶学委员会把酶分为七大类：氧化还原酶、转移酶、水解酶、裂合酶、异构酶、连接酶和转位酶，每种酶有 EC 编号。酶活性受温度、pH、抑制剂和激活剂影响。工业上酶用于洗涤剂、制糖、酿造、造纸和制药；阿诺德因酶的定向进化获 2018 年诺贝尔化学奖。许多药物是酶抑制剂，如阿司匹林抑制环氧合酶、他汀抑制 HMG-CoA 还原酶。

The Enzyme Commission divides enzymes into seven classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases and translocases, each with an EC number. Activity depends on temperature, pH, inhibitors and activators. Industry uses enzymes in detergents, sugar processing, brewing, paper and pharmaceuticals, and Frances Arnold received the 2018 Nobel Prize in Chemistry for the directed evolution of enzymes. Many drugs are enzyme inhibitors, such as aspirin (cyclooxygenase) and statins (HMG-CoA reductase).