Publisher Summary Glutathione (GSH) is the most important nonprotein thiol in living systems and is of widespread occurrence in the intracellular milieu of animals, plants, and microorganisms GSH was isolated and named by the English biochemist Frederick Gowland Hopkins This chapter discusses GSH status, the biologically relevant chemistry of GSH, the forms in which GSH can be present within the cell, along with the GSH content of cells and the methods for analysis of this substance GSH-related biochemical reactions and the biological roles of GSH are discussed in the chapter The use of perturbations in GSH status as a means for investigating GSH-related phenomena and an analysis of the consequences of perturbation are presented A short summary of genetic lesions related to GSH is also included Like chemically induced perturbations in GSH status, genetic lesions provide valuable insights into the role of GSH in normal functions and processes in cells The chapter concludes with some brief comments about the future of the relationship of GSH status to cellular processes

The Glutathione Status of Cells

There is significant evidence that, in living systems, free radicals and other reactive oxygen and nitrogen species play a double role, because they can cause oxidative damage and tissue dysfunction and serve as molecular signals activating stress responses that are beneficial to the organism. Mitochondria have been thought to both play a major role in tissue oxidative damage and dysfunction and provide protection against excessive tissue dysfunction through several mechanisms, including stimulation of opening of permeability transition pores. Until recently, the functional significance of ROS sources different from mitochondria has received lesser attention. However, the most recent data, besides confirming the mitochondrial role in tissue oxidative stress and protection, show interplay between mitochondria and other ROS cellular sources, so that activation of one can lead to activation of other sources. Thus, it is currently accepted that in various conditions all cellular sources of ROS provide significant contribution to processes that oxidatively damage tissues and assure their survival, through mechanisms such as autophagy and apoptosis.

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Role of ROS and RNS Sources in Physiological and Pathological Conditions

Perspectives in Nutrition is an introductory nutrition text appropriate for the majors and mixed majors nutrition courses. This student-focused text presents the major concepts in nutrition including the body's use of food nutrients and diet planning throughout the life cycle. The text places special emphasis on the application of nutrition principles in everyday life by exploring the health consequences of nutrition practices.

Perspectives in nutrition

Purification and properties of rat lung soluble glutathione peroxidase

Selenium (Se) is at once an essential and toxic nutrient that occurs in both inorganic and organic forms. The biological functions of Se are mediated through at least 13 selenoproteins that contain Se as selenocysteine (Se-cyst). The endogenous synthesis of this amino acid from inorganic Se (selenide Se-2) and serine is encoded by a stop codon UGA in mRNA and involves a unique tRNA. Selenium can also substitute for sulfur in methionine to form an analog, selenomethionine (Se-meth), which is the main form of Se found in food. Animals cannot synthesize Se-meth or distinguish it from methionine and as a result it is nonspecifically incorporated into a wide range of Se-containing proteins. The metabolic fate of Se varies according to the form ingested and the overall Se status of an individual. This paper reviews the bioavailability, including absorption, transport, metabolism, storage, and excretion, of the different forms of exogenous and endogenous Se.

Selenium metabolism and bioavailability.

SINCE 1957, selenium has been recognized as an essential micronutrient for animals, but its exact biological function has remained uncertain. The metabolic role of selenium in animals seems to be linked with vitamin E and sulphur amino acids1–4. Selenium has a sparing effect on vitamin E, and delays the onset of deficiency syndromes. Likewise, vitamin E and sulphur amino acids partially protect against or delay the onset of several forms of selenium deficiency syndromes. Rotruck et al.5 proposed that selenium functions as an integral part of glutathione (GSH) peroxidase, an enzyme that reduces toxic lipid peroxides to hydroxy acids6–8. They found that a large proportion of the 75Se from rat erythrocytes labelled in vivo remained with the enzyme during extensive purification, and more recently, their studies with highly purified GSH peroxidase have indicated that it contains approximately 4 mol of Se per mol of enzyme9. Similar findings were reported by Flohe et al. for bovine erythrocyte GSH peroxidase10. To learn more about the nutritional relationship between selenium and GSH peroxidase, we performed studies that showed GSH peroxidase activity is proportional to dietary selenium, which provided additional evidence for the role of selenium in the function of GSH peroxidase.

C. K. Chow

Papers

Glutathione peroxidase activity as a function of dietary selenomethionine