Definition

In biochemistry, a kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the substrate gains a phosphate group and the high-energy ATP molecule donates a phosphate group. This transesterification produces a phosphorylated substrate and ADP. Conversely, it is referred to as dephosphorylation when the phosphorylated substrate donates a phosphate group and ADP gains a phosphate group, producing a dephosphorylated substrate and the high energy molecules of ATP.

激酶是催化磷酸基团从含有磷酸的高能分子转移到特定底物的酶。该过程称为磷酸化：ATP给出磷酸基团，底物获得磷酸基团。最终底物磷酸化，ATP变成ADP。其相反过程称为去磷酸化（通常由磷酸酶介导）。

phosphorylase [fɒs'fɒrɪleɪz] n. [生化]磷酸化酶(catalyze the addition of inorganic phosphate groups to an acceptor)

phosphatase ['fɒsfəteɪz] n. [生化]磷酸酶(remove phosphate groups, i.e., dephosphorylation)

激酶与磷酸化酶（phosphorylase）、磷酸酶（phosphatase）区别：激酶是将高能分子如ATP中的磷酸转移到另一底物分子；磷酸化酶是将无机磷酸基团转移到底物分子；磷酸酶是催化除去分子中的磷酸基团。

Classification

Kinases are classified into broad groups by the substrate they act upon: protein kinases, lipid kinases, carbohydrates kinases, nucleoside kinase. Kinases can be found in a variety of species, from bacteria to mode to worms to mammals. More than 500 different kinases have been identified in humans. Specific kinases are often named after their substrates. Protein kinases often have multiple substrates, and proteins can serve as substrates for more than one specific kinase. For this reason, protein kinases are named based on what regulates their activity.

根据作用的底物，激酶可分为蛋白激酶、脂激酶、糖激酶、核苷酸激酶。在人中发现超过500中激酶。

蛋白激酶可对蛋白上含有羟基或氨基的残基进行磷酸化，常见的有丝氨酸、苏氨酸、酪氨酸、组氨酸，亦有色氨酸、天冬氨酸、谷氨酸。因此，可分为丝氨酸激酶、苏氨酸激酶、酪氨酸激酶、组氨酸激酶（Histidine protein kinases, HPK）等。

根据是否存在于细胞膜，酪氨酸激酶（tyrosine kinase，TK）分为受体酪氨酸激酶（receptor tyrosine kinases，RTKs）和胞质酪氨酸激酶（cytoplasmic protein tyrosine kinases）或非受体酪氨酸激酶。

RTKs是最大的酶联受体，既是受体，又是酶，还能同配体结合，将靶蛋白的酪氨酸残基磷酸化。截止2004年，发现了58种受体酪氨酸激酶，分为20个家族。受体酪氨酸激酶的胞外区是配体结合区，配体是可溶性或膜结合的多肽或蛋白类激素（包括胰岛素和多种生长因子）；胞内区是酪氨酸蛋白激酶的催化部位，具有自磷酸化位点。无信号分子存在时，RTK以无活性的单体存在。一旦信号分子与受体的配体结合区结合，两个单体分子发生二聚，受体尾部互相接触，激活蛋白激酶功能，使尾部酪氨酸残基磷酸化。磷酸化导致受体细胞内结构域尾部装配成信号复合物，成为胞内信号蛋白（可能有多种）的结合位点。与不同的信号蛋白结合，会引起不同信号的放大和转导。常见RTKs有表皮生长因子受体（epidermal growth factor receptor, EGFR）、血小板生长因子受体（platelet-derived growth factor receptor, PDGFR）、巨噬细胞集落刺激生长因子受体（macrophage colony stimulating factor receptor, M-CSFR）、胰岛素和胰岛素样生长因子-1受体（insulin and insulin-like growth factor-1 receptor, IGFR）、神经生长因子受体（nerve growth factor receptor, NGFR）、成纤维细胞生长因子受体（fibroblast growth factor receptor, FRFR）、血管内皮细胞生长因子受体（vascular endothelial growth factor, VEGFR）、肝细胞生长因子受体（hepatocyte growth factor, HGF）

非受体酪氨酸激酶（Non-receptor tyrosine kinases，nRTKs）约有10个家族：TEC、JAK、SRC、SYK、FAK、FES、FRK、ABL、ACK、CSK。

资料来源于百度和维基百科。