Localization of gamma-glutamylcysteine synthetase and glutathione synthetase activity in maize seedlings

• Published in: Plant physiology (Bethesda) Vol. 101; no. 2; pp. 561 - 566
• Main Authors: RÜEGSEGGER, A, BRUNOLD, C
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-02-1993
• Subjects: acide glutamique; acido glutamico; actividad enzimatica; activite enzymatique; Biological and medical sciences; Chloroplasts; cisteina; Corn; cysteine; Endosperm; Enzymes; enzymic activity; Fundamental and applied biological sciences. Psychology; glutamic acid; ligasas; ligase; ligases; Metabolism; Metabolism and Enzymology; Nitrogen metabolism; Peas; Plant physiology and development; Plant products; Plant roots; Plants; plantulas; plantule; Seedlings; Thiols; zea mays; Monocotyledones; Zea mays; Enzyme; Plastid; γ-Glutamylcysteine synthetase; Metabolism; Cereal crop; Glutathione synthetase; Enzymatic activity; Gramineae; Angiospermae; Plantlet; Spermatophyta; Developmental stage; Localization; Glutathione
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.101.2.561

Fresh weight, protein, cysteine, gamma-glutamylcysteine, glutathione, and the extractable activity of the enzymes of glutathione biosynthesis, gamma-glutamylcysteine synthetase (EC 6.3.2.2) and glutathione synthetase (EC 6.3.2.3), were measured in roots, scutella, endosperms, and shoots of 3-, 7-, and 11-d-old maize (Zea mays L. cv LG 9) seedlings. In 3-d-old seedlings, the scutella represented 14% of the seedling fresh weight, containing 43% of total protein and 63 and 55% of the activity of gamma-glutamylcysteine synthetase and glutathione synthetase, respectively; in 11-d-old seedlings, the corresponding values were 4.5% for fresh weight, 8.0% for protein content, and 14 and 20% for the enzyme activities. The highest concentrations of thiols were found for cysteine (0.27 mM) in the roots, for glutathione (4.4 mM) in the shoots, and for gamma-glutamylcysteine (13 micromolar) in the scutella of 3-d-old seedlings. The enzyme activities of roots were localized in subcellular fractions after sucrose density gradient centrifugation. Nearly half of the gamma-glutamylcysteine synthetase activity was detected in the root proplastids of 4-d-old seedlings, whereas < 10% of the glutathione synthetase activity was localized in this organelle. Our results demonstrate the importance of scutella in glutathione synthesis in the early stage of seedling development. Unlike chloroplasts, root plastids show only a small proportion of glutathione synthetase activity.