Serour Ehab, Antranikian Garabed
Technical University Hamburg-Harburg, Institute of Technical Microbiology, Hamburg, Germany.
Antonie Van Leeuwenhoek. 2002 Aug;81(1-4):73-83. doi: 10.1023/a:1020525525490.
The thermoacidophilic Archaea Thermoplasma acidophilum (optimal growth at 60 degrees C and pH 1-2), Picrophilus torridus and Picrophilus oshimae (optimal growth at 60 degrees C and pH 0.7) were able to utilize starch as sole carbon source. During growth these microorganisms secreted heat and acid-stable glucoamylases into the culture fluid. Applying SDS gel electrophoresis activity bands were detected with appearent molecular mass (Mw) of 141.0, 95.0 kDa for T. acidophilum, 133.0, 90.0 kDa for P. torridus and 140.0, 85.0 kDa for P. oshimae. The purified enzymes were incubated with various polymeric substrates such as starch, pullulan, panose and isomaltose. The product pattern, analyzed by HPLC, showed that in all cases glucose was formed as the sole product of hydrolysis. The purified glucoamylases were optimally active at pH 2.0 and 90 degrees C and have an isoelectric points (pI) between 4.5 and 4.8. Enzymatic activity was detected even at pH 1.0 and 100 degrees C. The glucoamylases were thermostable at elevated temperature with a half-life of 24 h at 90 degrees C for both P. torridus and T acidophilum, and 20 h at 90 degrees C for P oshimae. The enzyme system of T acidophilum has a lower Km value for soluble starch (1.06 mg/ml) than the enzymes from P. oshimae and P. torridus (4.35 mg/ml and 2.5 mg/ml), respectively. Enzyme activity was not affected by Na+, Mg++, Ca++, Ni++, Zn++, Fe++, EDTA and DTT.
嗜热嗜酸古菌嗜热栖热菌（在60℃和pH 1 - 2条件下生长最佳）、嗜热栖热嗜酸菌和大岛嗜热栖热嗜酸菌（在60℃和pH 0.7条件下生长最佳）能够利用淀粉作为唯一碳源。在生长过程中，这些微生物向培养液中分泌热稳定和酸稳定的糖化酶。应用SDS凝胶电泳检测到活性条带，嗜热栖热菌的表观分子量（Mw）为141.0、95.0 kDa，嗜热栖热嗜酸菌为133.0、90.0 kDa，大岛嗜热栖热嗜酸菌为140.0、85.0 kDa。将纯化的酶与各种聚合底物如淀粉、支链淀粉、潘糖和异麦芽糖一起孵育。通过HPLC分析产物模式表明，在所有情况下，葡萄糖都是水解的唯一产物。纯化的糖化酶在pH 2.0和90℃时活性最佳，等电点（pI）在4.5至4.8之间。即使在pH 1.0和100℃时也能检测到酶活性。嗜热栖热嗜酸菌和嗜热栖热菌的糖化酶在高温下具有热稳定性，在90℃下半衰期为24小时，大岛嗜热栖热嗜酸菌在90℃下半衰期为20小时。嗜热栖热菌的酶系统对可溶性淀粉的Km值（1.06 mg/ml）分别低于嗜热栖热嗜酸菌和嗜热栖热嗜酸菌的酶（4.35 mg/ml和2.5 mg/ml）。酶活性不受Na +、Mg ++、Ca ++、Ni ++、Zn ++、Fe ++、EDTA和DTT的影响。
