𝔖 Bobbio Scriptorium
✦   LIBER   ✦

Recycling of carbon in the oxidative pentose phosphate pathway in non-photosynthetic plastids

✍ Scribed by J. Hartwell; C. G. Bowsher; M. J. Emes

Publisher
Springer-Verlag
Year
1996
Tongue
English
Weight
673 KB
Volume
200
Category
Article
ISSN
0032-0935

No coin nor oath required. For personal study only.

✦ Synopsis

Recycling of carbon in the oxidative pentose phosphate pathway (OPPP) of intact pea root plastids has been studied. The synthesis of dihydroxyacetone phosphate (DHAP) and evolution of COz was followed in relation to nitrite reduction. A close coupling was observed between all three measured fluxes which were linear for up to 60 min and dependent upon the integrity of the plastids. However, the quantitative relationship between 1-~4CO2 evolution from glucose 6-phosphate and nitrite reduction varied with available hexose phosphate concentration. When 10 mM glucose 6-phosphate was supplied to intact plastids a stoichiometry of 1.35 was observed between 14C02 evolution and nitrite reduction.

As exogenous glucose 6-phosphate was decreased this value fell, becoming 0.47 in the presence of 0.2 mM glucose 6-phosphate, indicative of considerable recycling of carbon. This conclusion was reinforced when using [2-14C]glucose-6-phosphate. The measured release of 2-14C02 was consistent with the data for 1-t4C02, suggesting complete recycling of carbon in the OPPP. Ribose 5-phosphate was also able to support nitrite reduction and DHAP production. A stoichiometry of 2 NO2 reduced: 1 DHAP synthesised was observed at concentrations of 1 mM ribose 5-phosphate or less. At concentrations of ribose 5-phosphate greater than 1 mM this stoichiometry was lost as a result of enhanced DHAP synthesis without further increase in nitrite reduction. It is suggested that this decoupling from nitrite reduction is a function of excess substrate entering directly into the non-oxidative reactions of the OPPP, and may be useful when the demand for OPPP products is not linked to the demand for reductant. The significance of recycling in the OPPP is discussed in relation to the coordination of

πŸ“œ SIMILAR VOLUMES

Carbon metabolism of chloroplasts in the
Carbon metabolism of chloroplasts in the dark: Oxidative pentose phosphate cycle versus glycolytic pathway
✍ W. M. Kaiser; J. A. Bassham πŸ“‚ Article πŸ“… 1979 πŸ› Springer-Verlag 🌐 English βš– 736 KB

The conversion of U-labelled [14C]glucose-6-phosphate into other products by a soluble fraction oflysed spinach chloroplasts has been studied. It was found that both an oxidative pentose phosphate cycle and a glycolytic reaction sequence occur in this fraction. The formation of bisphosphates and of

In VivoDynamics of the Pentose Phosphate
In VivoDynamics of the Pentose Phosphate Pathway inSaccharomyces cerevisiae
✍ Sam Vaseghi; Anja Baumeister; Manfred Rizzi; Matthias Reuss πŸ“‚ Article πŸ“… 1999 πŸ› Elsevier Science 🌐 English βš– 396 KB

The in vivo dynamics of the pentose phosphate pathway has been studied with transient experiments in continuous culture of Saccaromyces cerevisiae. Rapid sampling was performed with a special sampling device after disturbing the steady state with a pulse of glucose. The time span of observation was