微生物低温酶适冷机制研究进展

Progress of Molecular Adaptation of Cold Enzymes from Microorganisms

地球寒冷生境中生存着大量微生物。它们必须在酶学水平上对低温导致的生理、生化变化进行调整 ,才能在极端环境中维持生命活力。低温导致化学反应速率下降 ,而低温酶可通过高周转率 (κcat)、高催化效率 (κcat Km)来弥补这种影响。低温酶的一些共性 ,包括低温条件 ( 0～30℃ )下催化活力较高、最适作用温度低、稳定性差以及活化能较低等 ,都可能与蛋白结构的高度柔顺性有关。与高温酶、中温酶相比 ,低温酶中涉及蛋白稳定性的结构因素以及弱相互作用 ,数量减少或发生改变。低温酶可能通过分子内相互作用的减弱、酶分子与溶剂间相互作用的增强 ,并经过适当的构象折叠 。

Numerous microorganisms have been found to have successfully colonized in cold environments of our planet.At the enzyme level,such microorganisms have to cope with the physiological and biochemical changes induced by low temperatures in order to maintain adequate metabolic fluxes.Cold enzymes compensate for the reduction of chemical reaction rates inherent to low temperatures by their high turnover number ( κ cat ) and catalytic efficiency ( κ cat / K m).General characters in common of cold enzymes including higher catalytic activity,lower optimum temperature for enzyme activity,lower stability and lower activation energy at low temperatures of 0～30℃,possibly originate from an increased flexibility of either a selected area of or the overall protein structure.Structural factor and weak interactions involved in protein stability are either reduced in number or modified in order to increase their flexibility when compared to mesophilic or thermophilic homologues.The molecular changes of cold enzymes tend to increase the flexibility of protein structure by a weakening of the intramolecular interactions and by an increase of the interactions with the solvent followed by appropriate folding process of protein conformation.