Subcellular distribution of gluconeogenetic enzymes in germinating castor bean endosperm

Journal Article · Sun Jul 01 04:00:00 EDT 1979 · Plant Physiol.; (United States)

DOI:https://doi.org/10.1104/pp.64.1.31· OSTI ID:5487919

Nishimura, M; Beevers, H

The intracellular distribution of enzymes capable of catalyzing the reactions from oxaloacetate to sucrose in germinating castor bean endosperm has been studied by sucrose density gradient centrifugation. One set of glycolytic enzyme activities was detected in the plastids and another in the cytosol. The percentages of their activities in the plastids were less than 10% of total activities except for aldolase and fructose diphosphatase. The activities of several of the enzymes present in the plastids seem to be too low to account for the in vivo rate of gluconeogenesis whereas those in the cytosol are quite adequate. Furthermore, phosphoenolypyruvate carboxykinase, sucrose phosphate synthetase, and sucrose synthetase, which catalyze the first and final steps in the conversion of oxaloacetate to sucrose, were found only in the cytosol. It is deduced that in germinating castor bean endosperm the complete conversion of oxaloacetate to sucrose and CO/sub 2/ occurs in the cytosol. The plastids contain some enzymes of the pentose phosphate pathway, pyruvate dehydrogenase and fatty acid synthetase in addition to the set of glycolytic enzymes. This suggests that the role of the plastid in the endosperm of germinating castor bean is the production of fatty acids from sugar phosphates, as it is known to be in the endosperm during seed development.

• Research Organization: Univ. of California, Santa Cruz
• OSTI ID: 5487919
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 64:1; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550300* -- Cytology
550800 -- Morphology
551000 -- Physiological Systems
59 BASIC BIOLOGICAL SCIENCES
BEANS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CASTOR
CENTRIFUGATION
CHALCOGENIDES
CHEMICAL REACTIONS
DECOMPOSITION
DISTRIBUTION
ENDOSPERM
ENZYMES
FOOD
GERMINATION
GLYCOLYSIS
IN VIVO
MEDICINAL PLANTS
MORPHOLOGY
OXIDES
OXYGEN COMPOUNDS
PLANT CELLS
PLANT TISSUES
PLANTS
SEPARATION PROCESSES
TISSUE DISTRIBUTION
VEGETABLES