Samland Anne K, Sprenger Georg A
The Institute of Microbiology, Universität Stuttgart, Allmandring 31, Stuttgart, Germany.
Int J Biochem Cell Biol. 2009 Jul;41(7):1482-94. doi: 10.1016/j.biocel.2009.02.001. Epub 2009 Feb 11.
The role of the enzyme transaldolase (TAL) in central metabolism, its biochemical properties, structure, and role in human disease is reviewed. The nearly ubiquitous enzyme transaldolase is a part of the pentose phosphate pathway and transfers a dihydroxyacetone group from donor compounds (fructose 6-phosphate or sedoheptulose 7-phosphate) to aldehyde acceptor compounds. The phylogeny of transaldolases shows that five subfamilies can be distinguished, three of them with proven TAL enzyme activity, one with unclear function, and the fifth subfamily comprises transaldolase-related enzymes, the recently discovered fructose 6-phosphate aldolases. The three-dimensional structure of a bacterial (Escherichia coli TAL B) and the human enzyme (TALDO1) has been solved. Based on the 3D-structure and mutagenesis studies, the reaction mechanism was deduced. The cofactor-less enzyme proceeds with a Schiff base intermediate (bound dihydroxyacetone). While a transaldolase deficiency is well tolerated in many microorganisms, it leads to severe symptoms in homozygous TAL-deficient human patients. The involvement of TAL in oxidative stress and apoptosis, in multiple sclerosis, and in cancer is discussed.
本文综述了转醛醇酶（TAL）在中心代谢中的作用、其生化特性、结构以及在人类疾病中的作用。几乎无处不在的转醛醇酶是磷酸戊糖途径的一部分，它将二羟基丙酮基团从供体化合物（6-磷酸果糖或景天庚酮糖7-磷酸）转移到醛受体化合物上。转醛醇酶的系统发育表明，可以区分出五个亚家族，其中三个具有已证实的TAL酶活性，一个功能尚不清楚，第五个亚家族包含与转醛醇酶相关的酶，即最近发现的6-磷酸果糖醛缩酶。已经解析了细菌（大肠杆菌TAL B）和人类酶（TALDO1）的三维结构。基于三维结构和诱变研究，推导了反应机制。无辅因子的酶通过席夫碱中间体（结合的二羟基丙酮）进行反应。虽然在许多微生物中转醛醇酶缺乏耐受性良好，但在纯合TAL缺乏的人类患者中会导致严重症状。本文还讨论了TAL在氧化应激、细胞凋亡、多发性硬化症和癌症中的作用。
