Gene amplification and cold adaptation of pepsin in Antarctic fish. A possible strategy for food digestion at low temperature
Gene amplification and cold adaptation of pepsin in Antarctic fish. A possible strategy for food digestion at low temperature
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DOI：
10.1016/j.gene.2004.04.030
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发表时间：
2004-07-21
期刊：
影响因子：
3.5
通讯作者：
Parisi, E
中科院分区：
文献类型：
--
作者：
Carginale, V;Trinchella, F;Parisi, E
冷适应生物在分子水平上发展了许多调整，以维持低温下的代谢功能。在其他特征中，它们可以产生以高转换数或高催化效率为特征的酶。本文旨在通过对南极鱼胃蛋白酶的研究，探讨南极鱼在低温条件下对食物的消化过程。为此目的，我们已经克隆和测序的三种形式的胃蛋白酶A和一个单一形式的胃蛋白酶从Trematomus bernacchii（岩鳕鱼）的胃粘膜。系统发育分析表明，这三种胃蛋白酶A同种型来自两个基因重复事件，导致最古老的胃蛋白酶A3和最新的胃蛋白酶A1和胃蛋白酶A2。分子建模已经揭示了这些酶与它们的嗜温对应物的显着结构差异。亲水性和灵活性上确定的南极和嗜温胃蛋白酶的底物结合subsites已显示胃蛋白酶A2减少亲水性和增加的灵活性，在底物裂缝的水平，特征典型的冷适应酶。来自鳕鱼胃粘膜的RNA与设计在不同胃蛋白酶形式的特定区域上的分子探针杂交的北方印迹分析显示鳕鱼胃蛋白酶基因以相当的水平表达。本研究结果表明，南极岩鳕在低温下采用了两种不同的策略来实现有效的蛋白质消化。一种机制是基因复制，其增加酶的产生以补偿降低的动力学效率，另一种机制是具有冷适应酶的典型特征的新酶的表达。(C)2004 Elsevier B.V.保留所有权利。
Cold-adapted organisms have developed a number of adjustments at the molecular level to maintain metabolic functions at low temperatures. Among other features, they can produce enzymes characterized by a high turnover number or a high catalytic efficiency. The present work is aimed at investigating the process of food digestion at low temperature through the study of pepsins in Antarctic notothenioids. For such a purpose, we have cloned and sequenced three forms of pepsin A and a single form of gastricsin from the gastric mucosa of Trematomus bernacchii (rock cod). Phylogenetic analysis has suggested that the three pepsin A isotypes arose from two gene duplication events leading to the most ancestral pepsin A3 and to the most recent forms represented by pepsin A1 and pepsin A2. Molecular modeling has unraveled significant structural differences in these enzymes with respect to their mesophilic counterparts. Hydropathy and flexibility determined on the substrate-binding subsites of Antarctic and mesophilic pepsins have shown for pepsin A2 reduced hydropathy and increased flexibility at the level of the substrate cleft, features typical of cold-adapted enzymes. Northern blot analysis of RNA from rock cod gastric mucosa hybridized with molecular probes designed on specific regions of different pepsin forms has shown that rock cod pepsin genes are expressed at comparable levels. The present results suggest that the Antarctic rock cod adopted two different strategies to accomplish efficient protein digestion at low temperature. One mechanism is the gene duplication that increases enzyme production to compensate for the reduced kinetic efficiency, the other is the expression of a new enzyme provided with features typical of cold-adapted enzymes. (C) 2004 Elsevier B.V. All rights reserved.