Sola-Penna M, Ferreira-Pereira A, Lemos A P, Meyer-Fernandes J R
Departamento de Fármacos, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Brasil.
Eur J Biochem. 1997 Aug 15;248(1):24-9. doi: 10.1111/j.1432-1033.1997.00024.x.
Baker's yeast cells accumulate osmolytes as a response to several stress conditions such as high-temperature and low-temperature shifts, dehydration, or osmotic stress. One of the major osmolytes that accumulates is trehalose, which plays an essential role affecting the survival of yeast at the time of stress. In this report, we show that trehalose efficiently protects the function and the structure of two yeast cytosolic enzymes against chemical denaturation by guanidinium chloride. Other sugars tested also protected yeast pyrophosphatase and glucose-6-phosphate dehydrogenase structure against guanidinium chloride effects, but were not as efficient at protecting enzyme activity. The thermostable pyrophosphatase from Bacillus stearothermophilus was also protected by several sugars against the chaotropic properties of guanidinium chloride, but was only protected by trehalose against functional inactivation. The function of the membrane-embedded H+-ATPase from yeast could not be protected by any of the tested sugars, although all of the sugars protected its structure from guanidinium-chloride-induced unfolding. The results presented in this study suggest that several sugars are able to prevent protein unfolding induced by a chaotropic compound. However, prevention of functional inactivation depends on the nature of the sugar. Trehalose was the most efficient, being able to protect many cytosolic enzymes against guanidinium chloride. The efficiency of protection also depended on the nature of the protein tested. This might explain why trehalose is one of the osmolytes accumulated in yeast and also why it is not the only osmolyte to accumulate.
面包酵母细胞会积累渗透调节物质，以应对多种应激条件，如高温和低温变化、脱水或渗透压应激。积累的主要渗透调节物质之一是海藻糖，它在应激时对酵母的存活起着至关重要的作用。在本报告中，我们表明海藻糖能有效保护两种酵母胞质酶的功能和结构，使其免受氯化胍的化学变性影响。所测试的其他糖类也能保护酵母焦磷酸酶和葡萄糖-6-磷酸脱氢酶的结构免受氯化胍的影响，但在保护酶活性方面效果不如海藻糖。嗜热脂肪芽孢杆菌的热稳定焦磷酸酶也受到几种糖类的保护，免受氯化胍的离液序列高的性质影响，但只有海藻糖能保护其功能不被失活。酵母膜嵌入的H⁺-ATP酶的功能不能被任何一种测试糖类保护，尽管所有糖类都能保护其结构不被氯化胍诱导展开。本研究结果表明，几种糖类能够防止由离液化合物诱导的蛋白质展开。然而，防止功能失活取决于糖类的性质。海藻糖是最有效的，能够保护许多胞质酶免受氯化胍的影响。保护效率还取决于所测试蛋白质的性质。这可能解释了为什么海藻糖是酵母中积累的渗透调节物质之一，也解释了为什么它不是唯一积累的渗透调节物质。
