Abstract：
A novel l-arabinose isomerase (L-AI) from Arthrobacter psychrolactophilus (Ap L-AI) was successfully cloned and characterized. The enzyme catalyzes the isomerization of d-galactose into a rare sugar d-tagatose. The recombinant Ap L-AI had an approximate molecular weight of about 258 kDa, suggesting it was an aggregate of five 58 kDa monomers and became the first record as a homo-pentamer L-AI. The catalytic efficiency (kcat/Km) and Km for d-galactose were 0.32 mM-1 min-1 and 51.43 mM, respectively, while for l-arabinose, were 0.64 mM-1 min-1 and 23.41 mM, respectively. It had the highest activity at pH 7.0-7.5 and 60 °C in the presence of 0.250 mM Mn2+. Ap L-AI was discovered to be an outstanding thermostable enzyme that only lost its half-life value at 60 °C for >1000 min. These findings suggest that l-arabinose isomerase from Arthrobacter psychrolactophilus is a promising candidate for d-tagatose mass-production due to its industrially competitive temperature.
摘要：
成功克隆并鉴定了来自嗜冷节杆菌（ApL-AI）的新型l-阿拉伯糖异构酶（L-AI）。该酶催化d-半乳糖异构化为稀有糖d-塔格糖。重组ApL-AI的分子量约为258kDa，表明它是五个58kDa单体的聚集体，并成为同五聚体L-AI的第一个记录。d-半乳糖的催化效率（kcat/Km）和Km分别为0.32mM-1min-1和51.43mM，分别,而对于l-阿拉伯糖，分别为0.64mM-1min-1和23.41mM，分别。在0.250mMMn2存在下，在pH7.0-7.5和60°C下具有最高的活性。发现ApL-AI是一种出色的热稳定酶，仅在60°C下>1000分钟失去其半衰期值。这些发现表明，嗜冷节杆菌的l-阿拉伯糖异构酶由于其具有工业竞争力的温度，是大量生产d-塔格糖的有希望的候选者。
