Glyceride metabolism and gluconeogenesis in barley endosperm |
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Authors: | Jonathan C. Newman Dennis E. Briggs |
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Affiliation: | Department of Biochemistry, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, England |
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Abstract: | Endosperms of quiescent barley grains contained, on average, 54.5 μg of neutral glyceride-glycerol, equivalent to ca 480 μg glyceride. Of this probably 90% was located in the aleurone layer. During germination the level of glyceride-glycerol declined. It also declined in degermed grains and aleurone layers incubated in vitro. The fall was accelerated by GA3, but indoleacetic acid, kinetin and glutamine were without effect. Increases in the levels of malate synthase and isocitrate lyase from very low initial values, and the results of incorporation studies with [14C]-labelled substrates, indicate that the glyoxylate cycle functions to convert glycerides to sucrose in germinating grains and degermed grains incubated with GA3, but not in degermed grains without the hormone. In the absence of GA3 the glyceride could be a respiratory substrate in degermed grains. The aleurone layers converted exogenous glucose to sucrose. Little label from [14C]-amino acids appeared in sucrose but in some cases considerable incorporation occurred into glutamine. |
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Keywords: | Gramineae barley endosperm gibberellic acid aleurone glycerides gluconeogenesis glutamine. |
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