Ciardiello M A, Camardella L, di Prisco G
Institute of Protein Biochemistry and Enzymology, C.N.R., Naples, Italy.
Biochim Biophys Acta. 1995 Jul 3;1250(1):76-82. doi: 10.1016/0167-4838(95)00046-w.
Glucose-6-phosphate dehydrogenase (G6PD) has been purified from the blood of two Antarctic teleost species, i.e., from the erythrocytes of Dissostichus mawsoni (family Nototheniidae), and from the plasma and cells of haemoglobinless Chionodraco hamatus (family Channichthyidae). The specific activities in haemolysates of Antarctic blood cells appear higher than that of a lysate of human erythrocytes. The two Antarctic enzymes have an apparent subunit molecular mass slightly higher than that of human G6PD; the electrophoretic behaviour on cellulose acetate is similar. Both Antarctic enzymes are irreversibly heat inactivated through a biphasic process. Km for glucose-6-phosphate (G6P) does not vary significantly with temperature, whereas Km for NADP increases at increasing temperature, kcat increases with temperature, with a break point at 35 degrees C (in human G6PD, the break point is at 15 degrees C). Thermodynamic and kinetic characterisation indicate that the catalytic performance of the enzyme of cold-adapted fish, at temperatures typical of their habitat, is more efficient than that displayed by G6PD from a temperature organism.
已从两种南极硬骨鱼的血液中纯化出葡萄糖-6-磷酸脱氢酶（G6PD），即从莫氏 Dissostichus mawsoni（南极鱼科）的红细胞中，以及从无血红蛋白的哈氏冰鱼 Chionodraco hamatus（冰鱼科）的血浆和细胞中。南极血细胞溶血产物中的比活性似乎高于人类红细胞裂解物中的比活性。这两种南极酶的表观亚基分子量略高于人类G6PD；在醋酸纤维素上的电泳行为相似。两种南极酶都通过双相过程不可逆地热失活。葡萄糖-6-磷酸（G6P）的Km值随温度变化不显著，而NADP的Km值随温度升高而增加，kcat随温度升高而增加，在35℃时有一个断点（在人类G6PD中，断点在15℃）。热力学和动力学表征表明，在适应低温鱼类的典型栖息地温度下，该酶的催化性能比来自温血动物的G6PD更有效。
