원문정보
초록
영어
A recombinant non-characterized protein previously proposed as putative l-rhamnose isomerase (RhaA) from Thermotoga maritima was purified by His-Trap affinity chromatography with a specific activity of 55 U/mg. The enzyme was identified as a single 46 kDa band on SDS-PAGE and the native enzyme was a tetramer with a molecular mass of 184 kDa by the gel filtration chromatography. The half-lives of the enzyme at 75, 80, 85, 90 and 95°C were 773, 347, 187, 118, and 65 h, respectively, indicating that it is the most thermostable of the known RhaAs. Among all aldopentoses and aldohexoses, RhaA displayed activity only with aldose substrates that possess hydroxyl groups oriented in the right-handed configuration at the C-2 and C-3 positions, such as L-rhamnose, L-lyxose, L-mannose, D-allose, D-gulose, and D-ribose in decreasing activity order. Under the optimum conditions of pH 8.0, 85°C, and 1 mM Mn2+, RhaA with 100 U enzyme/ml converted 500 L-xylulose/l to 225 g/l L-lyxose after 3 h, and converted 500 L-fructose/l to 175 g/l L-mannose after 5 h.