Are the Catalytic Properties of Enzymes from Piezophilic Organisms Pressure Adapted?
Are the Catalytic Properties of Enzymes from Piezophilic Organisms Pressure Adapted?
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DOI：
10.1002/cbic.200900367
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发表时间：
2009-09-21
期刊：
影响因子：
3.2
通讯作者：
Scrutton, Nigel S.
中科院分区：
文献类型：
--
作者：
Hay, Sam;Evans, Rhiannon M.;Scrutton, Nigel S.
本文报道了从深海2℃、280 bar环境中分离得到的嗜冷细菌深森氏菌二氢叶酸还原酶（DHFR）的晶体结构。该结构是典型的染色体DHFR，我们无法确定任何明显的结构特征，表明压力适应。特别是，该酶的核心区域几乎与来自嗜酸性大肠杆菌的DHFR相同。pH值为9时的稳态速率受大气压下氢化物转移的限制，在1 ~ 750 bar之间大致恒定，在更高的压力下下降。然而，k - m值随着压力的增加而增加，因此k(cat)/ k - m在整个压力范围内减小。同位素效应研究表明，压力的增加使反应的限速步骤发生了变化。因此，我们在这种酶的结构或活性中没有看到压力适应的证据。
We report the crystal structure of dihydrofolate reductase (DHFR) from the psychropiezophilic bacterium Moritella profunda, which was isolated from the deep ocean at 2 degrees C and 280 bar. The structure is typical of a chromosomal DHFR and we were unable to identify any obvious structural features that would suggest pressure adaptation. In particular, the core regions of the enzyme are virtually identical to those of the DHFR from the mesophile Escherichia coli. The steady-state rate at pH 9, which is limited by hydride transfer at atmospheric pressure, is roughly constant between I and 750 bar, falling at higher pressures. However, the value of K-M increases with increasing pressure, and as a result k(cat)/K-M decreases over the entire pressure range studied. Isotope effect studies showed that increasing the pressure causes a change in the rate-limiting step of the reaction. We therefore see no evidence of pressure adaptation in either the structure or the activity of this enzyme.