Grody W W, Dizikes G J, Cederbaum S D
Isozymes Curr Top Biol Med Res. 1987;13:181-214.
Studies in experimental animals and humans demonstrate the existence of two arginase isozymes. One, designated AI (or A1), has a high pI, is located in the cytosol, is most abundant in liver, and is thought to be primarily responsible for ammonia detoxification as urea. The gene coding for this isozyme is mutated in human hyperargininemia. A second isozyme, designated AII (or A4), has a neutral pI, is located in the mitochondrial matrix, and is thought to be involved primarily in the production of ornithine as a precursor of proline and glutamate. It appears to be expressed in most but not all tissues and in more nearly equal amounts. The two isozymes are immunologically distinct and are coded for by two separate genes. The great similarity in all measured kinetic and some physicochemical properties implies a high degree of structural similarity at the active site, but the lack of immunological cross-reactivity and DNA cross-hybridization implies substantial compositional differences in other parts of the enzyme molecules.
对实验动物和人类的研究表明存在两种精氨酸酶同工酶。一种被命名为AI（或A1），其pI值较高，位于胞质溶胶中，在肝脏中含量最为丰富，被认为主要负责将氨解毒为尿素。编码这种同工酶的基因在人类高精氨酸血症中发生突变。第二种同工酶被命名为AII（或A4），其pI值呈中性，位于线粒体基质中，被认为主要参与鸟氨酸的生成，鸟氨酸是脯氨酸和谷氨酸的前体。它似乎在大多数但并非所有组织中表达，且表达量更为接近。这两种同工酶在免疫上是不同的，由两个独立的基因编码。所有测得的动力学和一些物理化学性质的高度相似性意味着活性位点处具有高度的结构相似性，但缺乏免疫交叉反应性和DNA交叉杂交意味着酶分子其他部分存在显著的组成差异。
