Kitaoka Motomitsu, Matsuoka Yasuyuki, Mori Kiyotaka, Nishimoto Mamoru, Hayashi Kiyoshi
National Food Research Institute, National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.
Biosci Biotechnol Biochem. 2012;76(2):343-8. doi: 10.1271/bbb.110772. Epub 2012 Feb 7.
Bacterial laminaribiose phosphorylase (LBP(bac)) was first identified and purified from cell-free extract of Paenibacillus sp. YM-1. It phosphorolyzed laminaribiose into α-glucose 1-phosphate and glucose, but did not phosphorolyze other glucobioses. It slightly phosphorolyzed laminaritriose and higher laminarioligosaccharides. The specificity of the degree of polymerization of the substrate was clearly different from that of the enzyme of Euglena gracilis (LBP(Eug)): LBP(bac) was more specific to laminaribiose than LBP(Eug). It showed acceptor specificity in reverse phosphorolysis similar to LBP(Eug). Cloning of the gene encoding LBP(bac) (lbpA) has revealed that LBP(bac) is a member of the glucoside hydrolase family 94, which includes cellobiose phosphorylase, cellodextrin phosphorylase, and N,N'-diacetylchitobiose phosphorylase. The genes that encode the components of an ATP-binding cassette sugar transporter specific to laminarioligosaccharides were identified upstream of lbpA, suggesting that the role of LBP(bac) is to utilize laminaribiose generated outside the cell. This role is different from that of LBP(Eug), which participates in the utilization of paramylon, the intracellular storage 1,3-β-glucan.
细菌来源的昆布二糖磷酸化酶（LBP(bac)）最初是从芽孢杆菌属YM-1菌株的无细胞提取物中鉴定并纯化出来的。它能将昆布二糖磷酸解为α-葡萄糖1-磷酸和葡萄糖，但不能磷酸解其他葡萄糖二糖。它能轻微地磷酸解昆布三糖和更高聚合度的昆布寡糖。底物聚合度的特异性与纤细裸藻的酶（LBP(Eug)）明显不同：LBP(bac)对昆布二糖的特异性高于LBP(Eug)。在逆磷酸解反应中，它表现出与LBP(Eug)相似的受体特异性。编码LBP(bac)的基因（lbpA）的克隆表明，LBP(bac)是糖苷水解酶家族94的成员，该家族包括纤维二糖磷酸化酶、纤维糊精磷酸化酶和N,N'-二乙酰壳二糖磷酸化酶。在lbpA上游鉴定出了编码对昆布寡糖具有特异性的ATP结合盒式糖转运蛋白各组分的基因，这表明LBP(bac)的作用是利用细胞外产生的昆布二糖。这一作用与LBP(Eug)不同，LBP(Eug)参与细胞内储存的1,3-β-葡聚糖——副淀粉的利用。
