BACKGROUND Enzymatic isomerization is a promising strategy to solve the problem of xylose fermentation and, consequently, to leverage the production of advanced biofuels and biochemicals. In a previous work, our research group discovered a new strain of Streptomyces with great biotechnological potential due to its ability to produce a broad arsenal of enzymes related to lignocellulose degradation. METHODS We applied a multidisciplinary approach involving enzyme kinetics, biophysical methods, small angle X-ray scattering and X-ray crystallography to investigate two novel xylose isomerases, XylA1F1 and XylA2F1, from this strain. RESULTS We showed that while XylA1F1 prefers to act at lower temperatures and relatively lower pH, XylA2F1 is extremely stable at higher temperatures and presents a higher turnover number. Structural analysis revealed that XylA1F1 exhibits unique properties in the active site not observed in classical XylAs from classes I and II nor in its ortholog XylA2F1. It encompasses the natural substitutions, M86A and T93K, that create an extra room for substrate accommodation and narrow the active-site entrance, respectively. Such modifications may contribute to the functional differentiation of these enzymes. CONCLUSIONS We have characterized two novel xylose isomerases that display distinct functional behavior and harbor unprecedented amino-acid substitutions in the catalytic interface. GENERAL SIGNIFICANCE Our findings contribute to a better understanding of the functional and structural aspects of xylose isomerases, which might be instrumental for the valorization of the hemicellulosic fraction of vegetal biomass.

中文翻译：

---

一种来自链霉菌属的新型木糖异构酶的晶体结构。F-1揭示了与常规类别不同的​​独特功能。

背景技术酶异构化是解决木糖发酵问题并因此利用先进的生物燃料和生化物质生产的有前途的策略。在先前的工作中，我们的研究小组发现了一种具有巨大生物技术潜力的链霉菌新菌株，这是因为它能够产生与木质纤维素降解相关的广泛酶酶。方法我们采用了涉及酶动力学，生物物理方法，小角度X射线散射和X射线晶体学的多学科方法，研究了该菌株的两种新型木糖异构酶XylA1F1和XylA2F1。结果我们表明，虽然XylA1F1倾向于在较低的温度和相对较低的pH值下起作用，但XylA2F1在较高的温度下非常稳定，并且具有更高的周转率。结构分析表明，XylA1F1在活性位点上表现出独特的特性，而在I类和II类的经典XylA或其直系同源物XylA2F1中没有观察到。它涵盖了自然替代品M86A和T93K，它们分别为底物容纳提供了额外的空间并缩小了活动场所的入口。此类修饰可有助于这些酶的功能分化。结论我们已经表征了两种新颖的木糖异构酶，其表现出不同的功能行为并且在催化界面中具有空前的氨基酸取代。一般意义我们的发现有助于更好地理解木糖异构酶的功能和结构方面，这可能有助于植物生物量的半纤维素部分的增值。