The hyperthermophile Thermotoga maritima possesses d-amino acid-metabolizing enzymes and multifunctional enzymes associated with l- and d-amino acid metabolism, although it does not have typical alanine and glutamate racemases. Intriguingly, in this study, we found that unexpectedly one PLP fold-type I enzyme from this organism, TM1270, has six different enzyme activities, namely amino acid racemase, cystathionine β-lyase, serine dehydratase, threonine aldolase, aspartate 4-decarboxylase, and amino acid aminotransferase activities. We characterized the properties of these six enzyme activities including their substrate specificities, pH and temperature dependences, and kinetic parameters. β-Lyase activity was the highest among the six activities based on kinetic parameters. Furthermore, we determined the crystal structure of TM1270 with the internal aldimine form of pyridoxal 5′-phosphate, which forms a Schiff base with Lys202. The possible reaction mechanisms of the six enzyme activities are proposed based on the crystal structure and the results of mutational analysis.

中文翻译：

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来自超嗜热菌 Thermotoga maritima 的高度多功能酶 TM1270 的功能和结构分析


超嗜热菌 Thermotoga maritima 具有 d 氨基酸代谢酶和与 l 和 d 氨基酸代谢相关的多功能酶，尽管它没有典型的丙氨酸和谷氨酸消旋酶。有趣的是，在这项研究中，我们出乎意料地发现，来自该生物体的一种 PLP 折叠 I 型酶 TM1270 具有六种不同的酶活性，即氨基酸消旋酶、胱硫醚 β-裂解酶、丝氨酸脱水酶、苏氨酸醛缩酶、天冬氨酸 4-脱羧酶和氨基酸转氨酶活性。我们表征了这六种酶活性的性质，包括它们的底物特异性、pH 和温度依赖性以及动力学参数。根据动力学参数，β-Lyase 活性在六种活性中最高。此外，我们用吡哆醛 5′-磷酸盐的内部二胺形式确定了 TM1270 的晶体结构，它与 Lys202 形成希夫碱。根据晶体结构和突变分析结果，提出了六种酶活性的可能反应机制。