希少糖アロース代謝系酵素のX線結晶構造解析と生化学的解析 Structural and biochemical characterizations of enzymes involved in the metabolism of a rare sugar D-allose [通常講演]
神鳥成弘;塚本郁子
第96回⽇本⽣化学会⼤会 2023年10月 ポスター発表 福岡 ⽇本⽣化学会
D-Allose is a rare sugar, existing in very small amounts in nature, compared to D-glucose, D-mannose, and D-galactose. This is because D-allose has an axial hydroxy group at 3-position (O3) causing 1,3-diaxial interactions with H1/O1 and H5, which hinder a stable chair conformation. Interestingly, several bacteria have allose operon responsible for D-allose metabolism, which consists of seven genes, alsR, alsB, alsA, alsC, alsE, alsK, and rpiB. Repressor protein coded by alsR is thought to control gene expression. An extracellular allose-binding protein (AlsB), trans-membrane permease (AlsC), and an intracellular ATP binding protein (AlsA) construct an ABC transport system for import of D-allose. Allose kinase (AlsK) catalyzes the phosphorylation of D-allose to D-allose-6-phosphate (A6P), and D-ribose-5-phosphate isomerase B (RpiB) catalyzes the isomerization of A6P to D-allulose-6-phosphate (D-psicose-6-phosphate, P6P). Then, D-allulose-6-phospate 3-epimerase (AlsE) catalyzes the epimerization of P6P to D-fructose-6-phosphate (F6P), which can enter glycolysis. To understand the biological implication of allose operon utilizing a rare sugar D-allose, as a carbon source, we are conducting structural and biochemical characterizations of proteins coded in allose operon. Here, we report X-ray structures of AlsK, RpiB, and AlsE from Paenibacillus kribbensis (Pkb), and enzyme activity assays of PkbAlsK. The results showed that PkbAlsK could specifically recognize D-allose as a substrate with a high enzyme activity, and that F6P could be obtained from D-allose as a starting material by PkbAlsK, PkbRpiB, and PkbAlsE.