PDF(Pubmed)
Abstract：
Living organisms ranging from bacteria to animals have developed their own ways to accumulate and store phosphate during evolution, in particular as the polyphosphate (polyP) granules in bacteria. Degradation of polyP into phosphate is involved in phosphorus cycling, and exopolyphosphatase (PPX) is the key enzyme for polyP degradation in bacteria. Thus, understanding the structure basis of PPX is crucial to reveal the polyP degradation mechanism. Here, it is found that PPX structure varies in the length of ɑ-helical interdomain linker (ɑ-linker) across various bacteria, which is negatively correlated with their enzymatic activity and thermostability - those with shorter ɑ-linkers demonstrate higher polyP degradation ability. Moreover, the artificial DrPPX mutants with shorter ɑ-linker tend to have more compact pockets for polyP binding and stronger subunit interactions, as well as higher enzymatic efficiency (kcat/Km) than that of DrPPX wild type. In Deinococcus-Thermus, the PPXs from thermophilic species possess a shorter ɑ-linker and retain their catalytic ability at high temperatures (70 °C), which may facilitate the thermophilic species to utilize polyP in high-temperature environments. These findings provide insights into the interdomain linker length-dependent evolution of PPXs, which shed light on enzymatic adaption for phosphorus cycling during natural evolution and rational design of enzyme.
摘要：
从细菌到动物的活生物体已经发展出了在进化过程中积累和储存磷酸盐的方式，特别是作为细菌中的多磷酸盐(polyP)颗粒。polyP降解为磷酸盐参与磷循环，外聚磷酸酶（PPX）是细菌中降解polyP的关键酶。因此，了解PPX的结构基础对于揭示polyP降解机理至关重要。这里,发现PPX的结构在各种细菌中，在α-螺旋域间接头(α-linker)的长度上是不同的，这与它们的酶活性和热稳定性呈负相关-具有较短α-接头的那些具有较高的polyP降解能力。此外，人工DrPPX突变体与较短的α-接头往往有更紧凑的口袋polyP结合和更强的亚基相互作用，以及比DrPPX野生型更高的酶效率(kcat/Km)。在异常球菌，来自嗜热物种的PPX具有较短的α-接头，并在高温（70°C）下保持其催化能力，这可以促进嗜热物种在高温环境中利用polyP。这些发现为PPX的域间接头长度依赖性进化提供了见解，阐明了自然进化过程中磷循环的酶适应和酶的合理设计。
