Kidron Heidi, Repo Susanna, Johnson Mark S, Salminen Tiina A
Department of Biochemistry and Pharmacy, Abo Akademi University, Turku, Finland.
Mol Biol Evol. 2007 Jan;24(1):79-89. doi: 10.1093/molbev/msl133. Epub 2006 Sep 22.
Arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) are involved in the biosynthesis of putrescine, which is the precursor of other polyamines in animals, plants, and bacteria. These pyridoxal-5'-phosphate-dependent decarboxylases belong to the alanine racemase (AR) structural family together with diaminopimelate decarboxylase (DapDC), which catalyzes the final step of lysine biosynthesis in bacteria. We have constructed a multiple-sequence alignment of decarboxylases in the AR structural family and, based on the alignment, inferred phylogenetic trees. The phylogenetic tree consists of 3 distinct clades formed by ADC, DapDC, and ODC that diverged from an ancestral decarboxylase. The ancestral decarboxylase probably was able to recognize several substrates, and in archaea and bacteria, ODC may have retained the ability to bind other amino acids. Previously, a paralogue of ODC has been proposed to account for ADC activity detected in mammalian cells. According to our results, this appears unlikely, emphasizing the need for more caution in functional assignment made using sequence data and illustrating the continuing value of phylogenetic analysis in clarifying relationships and putative functions.
精氨酸脱羧酶（ADC）和鸟氨酸脱羧酶（ODC）参与腐胺的生物合成，腐胺是动物、植物和细菌中其他多胺的前体。这些依赖磷酸吡哆醛的脱羧酶与二氨基庚二酸脱羧酶（DapDC）一起属于丙氨酸消旋酶（AR）结构家族，DapDC催化细菌中赖氨酸生物合成的最后一步。我们构建了AR结构家族中脱羧酶的多序列比对，并基于该比对推断了系统发育树。系统发育树由ADC、DapDC和ODC形成的3个不同分支组成，它们从一个祖先脱羧酶分化而来。祖先脱羧酶可能能够识别几种底物，在古细菌和细菌中，ODC可能保留了结合其他氨基酸的能力。以前，有人提出ODC的一个旁系同源物可解释在哺乳动物细胞中检测到的ADC活性。根据我们的结果，这种情况似乎不太可能，这强调了在使用序列数据进行功能分配时需要更加谨慎，并说明了系统发育分析在阐明关系和推定功能方面的持续价值。
