Psychrophilic enzymes are generally active at low temperatures, and their functions have attracted much interest in food processing, biochemical research, and chemical industry. However, their activities are usually lost above their growth temperature because of their flexible and unstable structure. Here, we unexpectedly found that a homodimeric NADP-dependent malic enzyme from a psychrophilic bacterium, Shewanella livingstonensis Ac10 (SL-ME) showed sufficient activity with 60°C treatment, similar to its counterpart from mesophilic Escherichia coli (MaeB). Consistently, SL-ME and MaeB irreversibly denatured at 71.9°C and 64.5°C, respectively. Therefore, SL-ME shows robust catalytic activity, which appears to be advantageous for its application in the bioconversion of NADP to NADPH, an essential ingredient for membrane phospholipid synthesis.

嗜冷酶通常在低温下具有活性，其功能在食品加工、生化研究和化学工业中引起了极大的兴趣。然而，由于其柔性和不稳定的结构，它们的活性通常在高于其生长温度时就会丧失。在这里，我们意外地发现来自嗜冷细菌Shewanella livingstonensis Ac10 (SL-ME)的同源二聚体 NADP 依赖性苹果酸酶在60°C 处理下表现出足够的活性，类似于来自嗜温大肠杆菌的对应物(梅B)。一致地，SL-ME 和 MaeB 分别在 71.9°C 和 64.5°C 不可逆地变性。因此，SL-ME 显示出强大的催化活性，这似乎有利于其在 NADP 生物转化为 NADPH（膜磷脂合成的必需成分）中的应用。