对深海适冷菌Pseudomonas sp.SM9915分泌不同适冷蛋白酶的研究

STUDY ON THE DIFFERENT COLD-ADAPTED PROTEASE PRODUCED BY THE DEEPSEA PSYCHROTROPHIC BACTERIUM PSEUDOMONAS SP. SM9915

从 1 8 5 5m深的海底泥样中分离到一株产适冷蛋白酶的适冷菌Pseudomonassp .SM991 5 ,经测定发现该菌株的最适生长温度为 2 0℃ ,最适产酶温度为 1 5℃ ,粗蛋白酶的最适酶活温度为 40℃。在此基础上 ,采用硫酸铵沉淀和分子筛层析方法对P .sp.SM991 5分泌的蛋白酶进行了分离纯化。结果表明 ,P .sp .SM991 5至少分泌三种适冷蛋白酶 ,并且三种蛋白酶的性质有所不同。这三种蛋白酶的最适pH分别为 8.0、9.0、7.0。最适酶活温度分别为45℃、40℃、40℃ ;其热稳定性也有明显的差别 ,40℃下保温 ,酶活的半衰期分别为 1 1min、5min和 2 7min ,表明这三种蛋白酶对低温的适应进化是不同步的。

A psychrotrophic strain Pseudomonas sp. SM9915 excreting cold adapted proteases was isolated from 1855 meter deep sea silt. The optimum temperature for growth was about 20℃, otherwise, the highest specific synthetic rate of the protease occurred at about 15℃. The optimum temperature of the crude protease for casein catalysis was 40℃. The cold adapted protease was purified. The results showed that P . sp. SM9915 at least produced three kinds of proteases. The optimum pH of the proteases was 8.0, 9.0 and 7.0, respectively. The optimum temperature of the three kinds of proteases for casein catalysis were 45℃, 40℃ and 40℃, respectively. All the three kinds of the proteases were susceptible to heat treatment, and the half time for the decrease of protease activity was 11 minutes, 5 minutes, 27 minutes, respectively, when incubated at 40℃, which was showed that the cold adapted evolution of the three kinds of the protease was not synchronous.