Kusakabe T, Motoki K, Sugimoto Y, Hori K
Department of Biochemistry, Saga Medical School, Japan.
Comp Biochem Physiol B Biochem Mol Biol. 1998 Aug;120(4):665-73. doi: 10.1016/s0305-0491(98)10060-3.
To assess which regions of the aldolase C molecule are required for exhibiting isozyme-specific kinetic properties, we have constructed nine chimeric enzymes of human aldolases A and C. Kinetic studies of these chimeric enzymes revealed that aldolase C absolutely required its own isozyme group-specific sequences (IGS), particularly IGS-4, for exhibiting the characteristics of aldolase C which differ significantly from those of isozymes A and B (Kusakabe T, Motoki K, Hori K. Human aldolase C: characterization of the recombinant enzyme expressed in Escherichia coli. J Biochem (Tokyo) 1994;115:1172-7). Whereas human aldolases A and B required their own isozyme group-specific sequences-1 and -4 (IGS-1 and -4) as the main determinants of isozyme-specific kinetic properties (Motoki K, Kitajima Y, Hori K. Isozyme-specific modules on human aldolase A molecule. J Biol Chem 1993;268:1677-83; Kusakabe T, Motoki K, Sugimoto Y, Takasaki Y, Hori K. Human aldolase B: liver-specific properties of the isoenzyme depend on type B isozyme group-specific sequence. Prot. Eng. 1994;7:1387-93), the present studies indicate that the IGS-1 is principally substitutable between aldolases A and C. The kinetic data also suggests that the connector-2 (amino acid residues 243-306) may modulate the interaction of IGS units with the alpha/beta barrel of the aldolase molecule.
为了评估醛缩酶C分子的哪些区域对于展现同工酶特异性动力学特性是必需的，我们构建了9种人醛缩酶A和C的嵌合酶。对这些嵌合酶的动力学研究表明，醛缩酶C展现出与同工酶A和B显著不同的醛缩酶C的特性时，绝对需要其自身的同工酶组特异性序列（IGS），尤其是IGS-4（楠部彻、元木克、堀 晃。人醛缩酶C：在大肠杆菌中表达的重组酶的特性。《东京生物化学杂志》1994年；115：1172 - 1177）。而人醛缩酶A和B需要它们自身的同工酶组特异性序列-1和-4（IGS-1和-4）作为同工酶特异性动力学特性的主要决定因素（元木克、北岛洋、堀 晃。人醛缩酶A分子上的同工酶特异性模块。《生物化学杂志》1993年；268：1677 - 1683；楠部彻、元木克、杉本洋、高崎洋、堀 晃。人醛缩酶B：同工酶的肝脏特异性特性取决于B型同工酶组特异性序列。《蛋白质工程》1994年；7：1387 - 1393），目前的研究表明IGS-1在醛缩酶A和C之间主要是可替换的。动力学数据还表明，连接体2（氨基酸残基243 - 306）可能调节IGS单元与醛缩酶分子的α/β桶之间的相互作用。
