酶

Enzymes are biomolecules that catalyze (ie, increase the rates of) chemical reactions.Nearly all known enzymes are proteins.酶是催化（即增加化学反应的速率）的生物分子。几乎所有已知的酶都是蛋白质。 However, certain RNA molecules can be effective biocatalysts too.但是，某些RNA分子也可以是有效的生物催化剂。 These RNA molecules have come to be known as ribozymes.这些RNA分子已被称为核酶。 In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products.在酶促反应中，过程开始时的分子称为底物，酶将其转化为不同的分子，称为产物。 Almost all processes in a biological cell need enzymes to occur at significant rates.生物细胞中几乎所有过程都需要酶以显着速率发生。 Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.由于酶对它们的底物具有选择性，并且在许多可能性中仅加速了少数反应，因此细胞中产生的一组酶决定了该细胞中发生哪些代谢途径。
Like all catalysts, enzymes work by lowering the activation energy (Ea or ΔG?) for a reaction, thus dramatically increasing the rate of the reaction.像所有催化剂一样，酶通过降低反应的活化能（Ea或ΔGXNUMX）起作用，从而大大提高了反应速率。 Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions.大多数酶反应速率比可比的未催化反应快几百万倍。