Reserve carbohydrates maintain the viability of Saccharomyces cerevisiae cells during chronological aging

Glycogen and trehalose are well known to participate in many important cell functions, e.g., protection from stress factors, regulation of cell growth and division, spore formation. Since the aging is a complex process involving many aspects of cell metabolism, it was interesting to study the role of glycogen and trehalose in maintenance of viability of aging cells. We have revealed that cell aging is accompanied by an abrupt fall of glycogen and trehalose contents between the second and third weeks of aging. Simultaneously, we observed a decrease in the activity of glycolytic enzymes, phosphofructokinase and hexokinase. At the same time, the viability of aging cells abruptly declined. Although we found neither glycogen nor trehalose in the cells after the third week of aging, they remained viable for some time, apparently due to development of some compensatory metabolic pathways. In spite of this fact, complete death of the cells occurred by the eighth week of experiment, which confirmed irreplaceability of reserve carbohydrates in yeast cell metabolism. Possible reasons of the inability of aging cells to accumulate glycogen and trehalose are discussed in the work. (C) 2004 Elsevier Ireland Ltd. All rights reserved.