Department of Bioscience and Biotechnology, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea.
J Biosci Bioeng. 2010 Jul;110(1):26-31. doi: 10.1016/j.jbiosc.2009.12.011. Epub 2010 Jan 27.
The specific activity and catalytic efficiency (k(cat)/K(m)) of the recombinant putative protein from Providencia stuartii was the highest for D-lyxose among the aldose substrates, indicating that it is a D-lyxose isomerase. Gel filtration analysis suggested that the native enzyme is a dimer with a molecular mass of 44 kDa. The maximal activity for D-lyxose isomerization was observed at pH 7.5 and 45 degrees C in the presence of 1 mM Mn(2+). The enzyme exhibited high isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration, such as D-lyxose, D-mannose, L-ribose, D-talose, and L-allose (listed in decreasing order of activity). The enzyme exhibited the highest activity for D-xylulose among all pentoses and hexoses. Thus, D-lyxose was produced at 288 g/l from 500 g/l D-xylulose by D-lyxose isomerase at pH 7.5 and 45 degrees C for 2 h, with a conversion yield of 58% and a volumetric productivity of 144 g l(-1) h(-1). The observed k(cat)/K(m) (920 mM(-1) s(-1)) of P. stuartiid-lyxose isomerase for D-xylulose is higher than any of the k(cat)/K(m) values previously reported for sugar and sugar phosphate isomerases with monosaccharide substrates. These results suggest that the enzyme will be useful as an industrial producer of D-lyxose.
从产吲哚假单胞菌中分离得到的重组推定蛋白对醛糖底物中的 D-来苏糖的比活性和催化效率 (k(cat)/K(m)) 最高，表明它是一种 D-来苏糖异构酶。凝胶过滤分析表明，天然酶是一种二聚体，分子量为 44 kDa。在 pH 7.5 和 45°C 下，在 1 mM Mn(2+)存在的情况下，D-来苏糖异构化的最大活性。该酶对 C2 和 C3 羟基处于左手构型的醛糖底物具有很高的异构化活性，如 D-来苏糖、D-甘露糖、L-核糖、D-塔罗糖和 L-阿洛糖（活性依次降低）。该酶对所有戊糖和己糖中 D-木酮糖的活性最高。因此，在 pH 7.5 和 45°C 下，D-木酮糖经 D-来苏糖异构酶作用 2 小时，可从 500 g/L D-木酮糖中生产 288 g/L D-来苏糖，转化率为 58%，体积产率为 144 g/L·h。观察到的 P. stuartii-D-来苏糖异构酶对 D-木酮糖的 k(cat)/K(m)（920 mM(-1) s(-1)）高于之前报道的具有单糖底物的糖和糖磷酸异构酶的任何 k(cat)/K(m) 值。这些结果表明，该酶将作为 D-来苏糖的工业生产酶具有应用价值。
