Carbohydrate oxidation by leucoplasts from suspension cultures of soybean (Glycine maxL.)

✍ Scribed by Stephen A. Coates; Tom ap Rees

• Publisher: Springer-Verlag
• Year: 1993
• Tongue: English
• Weight: 654 KB
• Volume: 189
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00198214

✦ Synopsis

The aim of this work was to discover how leucoplasts from suspension cultures of soybean (Glycine max L.) oxidize hexose monophosphates. Leucoplasts were isolated from protoplast lysates on a continuous gradient of Nycodenz with a yield of 28% and an intactness of 80%. Incubation of the leucoplasts with 14C-labelled substrates led to 14CO2 production, that was dependent upon leucoplast intactness, from [U-14C]glucose 6-phosphate, [U-~4C]glucose 1-phosphate, [U-~4C] fructose 6-phosphate and [U-14C]glucose + ATP, but not from [U-14C]fructose-l,6-bisphosphate or [U-~4C]triose phosphate. The yield from [U-~4C]glucose 6-phosphate was at least four times greater than that from any of the other substrates. When [1-14C] -, [2-14C] -, [3,4-~4C]-, and [6-~4C]glucose 6-phosphate were supplied to leucoplasts significant 14C02 production that was dependent upon leucoplast intactness was found only for [1-~4C]glucose 6-phosphate. It is argued that soybean cell leucoplasts oxidize glucose 6-phosphate via the oxidative pentose phosphate pathway with very little recycling, and that in these plastids glycolysis to acetyl CoA is negligible.