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Subcellular Compartmentation of the 4-Aminobutyrate Shunt in Protoplasts from Developing Soybean Cotyledons
K. E. Breitkreuz1, B. J. Shelp
1Department of Horticultural Science and Interdepartmental Plant Physiology Program, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Abstract:
The subcellular localization of enzymes involved in the 4-ami-nobutyrate shunt was investigated in protoplasts prepared from developing soybean [Glycine max (L.) Merrill cv Maple Arrow] cotyledons. Protoplast lysate was fractionated by differential and continuous Percoll-gradient centrifugation to separate organelle fractions. Glutamate decarboxylase (EC 4.1.1.15) was found exclusively in the cytosol, whereas 4-aminobutyrate:pyruvate transami-nase (EC 2.6.1.19) and succinic semialdehyde dehydrogenase (EC 1.2.1.16) were associated exclusively with the mitochondrial fractions. Mitochondrial fractions also catabolized [U-14C]4-aminobu-tyrate to labeled succinate.