Department of Plant Physiology, Umeå Plant Science Centre, Umeå University, 90187 Umeå, Sweden.
Diamyd Medical, 90621 Umeå, Sweden.
Int J Mol Sci. 2023 May 17;24(10):8914. doi: 10.3390/ijms24108914.
UDP-glucose (UDPG) pyrophosphorylase (UGPase) catalyzes a reversible reaction, producing UDPG, which serves as an essential precursor for hundreds of glycosyltransferases in all organisms. In this study, activities of purified UGPases from sugarcane and barley were found to be reversibly redox modulated in vitro through oxidation by hydrogen peroxide or oxidized glutathione (GSSG) and through reduction by dithiothreitol or glutathione. Generally, while oxidative treatment decreased UGPase activity, a subsequent reduction restored the activity. The oxidized enzyme had increased values with substrates, especially pyrophosphate. The increased values were also observed, regardless of redox status, for UGPase cysteine mutants (Cys102Ser and Cys99Ser for sugarcane and barley UGPases, respectively). However, activities and substrate affinities (s) of sugarcane Cys102Ser mutant, but not barley Cys99Ser, were still prone to redox modulation. The data suggest that plant UGPase is subject to redox control primarily via changes in the redox status of a single cysteine. Other cysteines may also, to some extent, contribute to UGPase redox status, as seen for sugarcane enzymes. The results are discussed with respect to earlier reported details of redox modulation of eukaryotic UGPases and regarding the structure/function properties of these proteins.
UDP-葡萄糖（UDPG）焦磷酸化酶（UGPase）催化一个可逆反应，产生 UDPG，它是所有生物体中数百种糖基转移酶的重要前体。在这项研究中，发现来自甘蔗和大麦的纯化 UGPase 的活性在体外可通过过氧化氢或氧化型谷胱甘肽（GSSG）的氧化以及通过二硫苏糖醇或谷胱甘肽的还原而被可逆地氧化还原调节。一般来说，虽然氧化处理会降低 UGPase 的活性，但随后的还原会恢复其活性。与底物（特别是焦磷酸）相比，氧化酶的 值增加。无论氧化还原状态如何，UGPase 半胱氨酸突变体（分别为甘蔗和大麦 UGPase 的 Cys102Ser 和 Cys99Ser）也观察到了增加的 值。然而，甘蔗 Cys102Ser 突变体的活性和底物亲和力（s）仍然容易受到氧化还原调节，而大麦 Cys99Ser 则不然。数据表明，植物 UGPase 主要通过单个半胱氨酸的氧化还原状态的变化受到氧化还原控制。其他半胱氨酸也可能在一定程度上影响 UGPase 的氧化还原状态，如甘蔗酶所示。结果与先前报道的真核 UGPase 氧化还原调节的详细信息以及这些蛋白质的结构/功能特性进行了讨论。
