Ulbrich R
Biotechnikum, Martin-Luther Universität Halle-Wittenberg, Halle, DDR.
Biomed Biochim Acta. 1988;47(9):821-30.
alpha-Amylases from B. licheniformis and A. oryzae, which differ in their thermal stability, were studied with respect to their resistance to chemical denaturants as guanidine hydrochloride, urea, aliphatic alcohols, and formaldehyde. Moreover, the thermal and chemical stabilities of both enzymes were compared after their covalent binding to gamma-aminopropyl silica. The thermolabile alpha-amylase (A. oryzae) as well as the thermostable alpha-amylase (B. licheniformis) are remarkably stabilized by immobilization. Therefore, the high thermal resistance of the thermophilic enzyme may be further increased. Soluble and immobilized alpha-amylases from B. licheniformis are more resistant to guanidine hydrochloride, urea, methanol, ethanol, propranol, and t-butanol than the alpha-amylases from A. oryzae. Obviously, the high intrinsic stability of the thermophilic enzyme is also valid for chemical denaturation. An exception is given by the effect of formaldehyde, which may result in chemical modifications of the protein molecule. Enzymes from B. licheniformis are more sensitive against formaldehyde than those from A. oryzae. As in thermal inactivation, immobilization protects alpha-amylase from A. oryzae against denaturation by guanidine hydrochloride and urea, but fails in the denaturation by alcohols. Therefore, stabilizing effects in immobilized enzymes are dependent on the kind of denaturant.
研究了来自地衣芽孢杆菌和米曲霉的α-淀粉酶，它们的热稳定性不同，考察了它们对化学变性剂如盐酸胍、尿素、脂肪醇和甲醛的抗性。此外，还比较了两种酶共价结合到γ-氨丙基硅胶上后的热稳定性和化学稳定性。热不稳定的α-淀粉酶（米曲霉）以及热稳定的α-淀粉酶（地衣芽孢杆菌）通过固定化显著稳定。因此，嗜热酶的高热抗性可能会进一步提高。与米曲霉的α-淀粉酶相比，地衣芽孢杆菌的可溶性和固定化α-淀粉酶对盐酸胍、尿素、甲醇、乙醇、丙醇和叔丁醇更具抗性。显然，嗜热酶的高固有稳定性在化学变性方面也成立。甲醛的作用是个例外，它可能导致蛋白质分子的化学修饰。地衣芽孢杆菌的酶比米曲霉的酶对甲醛更敏感。与热失活一样，固定化保护米曲霉的α-淀粉酶免受盐酸胍和尿素的变性作用，但对醇类变性作用无效。因此，固定化酶中的稳定作用取决于变性剂的种类。
