Intermediates of the Pentose Phosphate Pathway as Respiratory Substrates.

Beevers, Harry

doi:10.1104/pp.31.5.339

Cited by 36 publications

(19 citation statements)

References 8 publications

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Role of Hexose Monophosphate Pathway in Tomato Catabolism

Wang¹,

Doyle²,

Ramsey³

1962

Plant Physiol.

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The operation of the hexose monophosphate pathway (HMP) in plants has been the object of extensive studies in recent years (1,2,4). In previous papers (3,9) it has been demonstrated that in intact tomato fruit, glucose is catabolized mainly by way of the Embden-Meyerhof-Parnas pathway (EMP) and to a limited extent via the HMP pathway. However, the catabolic fate of the pentose phosphate, derived from glucose via the HMP pathway, remains to be elucidated. The latter problem is an important one since one of the assumptions made in deriving equations for pathway estimation is that the pentose phosphate does not participate significantly in fruit respiration (3). Subsequently, from radiorespirometric studies of gluconate catabolism in tomato fruit (9) it is revealed that C-2, C-3,4, and C-6 of gluconate, in addition to C-1. were converted to some extent to respiratory CO, a fact indicating that the pentose phosphate derived from glucose via phosphogluconate was, indeed, engaged in respiratory functions.In the present work, the incorporation of gluconate-2-C14, gluconate-6-C14, and ribose-1-C14 into fruit constituents, particularly that into the fruit glucose molecules, has been studied. The isotopic distribution patterns in fruit glucose derived from the respectively labeled substrates, enables one to gain considerable insight into the catabolic mechanism responsible for the conversion of the carbon atoms of pentose phosphate to respiratory CO.,. The Materials & MethodsThe tomato fruit used in the present experiments were of the Michigan State Forcing variety and were selected on the same basis as described in earlier work (3, 9).1 Carbon-14 Labeled Substrates: Gluconate-1-C14 was purchased from the Nuclear-Chicago Corp. Gluconate-2, and -6-C14 were prepared from the correspondingly labeled glucose samples by the method of

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confidence: 99%

Role of Hexose Monophosphate Pathway in Tomato Catabolism

Wang¹,

Doyle²,

Ramsey³

1962

Plant Physiol.

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“…The latter, upon equilibration with the triose plhosphate metabolism of the leaf would give rise to the observed D-glucose labeled primarily in carbons 1, 3, 4, and 6 (5). The slightly greater amount of label in C-2 than in C-5 would be a consequience of pentose phosphalte metabolism (1,4).…”

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“…It had a specific activity of 100,000 cpm per mg of carbon as determined bv wet combustion of an aliquot after dilution with unlabeled D-glucose. (1,6). The latter, upon equilibration with the triose plhosphate metabolism of the leaf would give rise to the observed D-glucose labeled primarily in carbons 1, 3, 4, and 6 (5).…”

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confidence: 99%

Observations on the Incorporation of C¹⁴ into Tartaric Acid and the Labeling Pattern of D-Glucose from an Excised Grape Leaf Administered L-Ascorbic Acid-6-C¹⁴.

Loewus¹,

Stafford²

1958

Plant Physiol.

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“…As the labeling data show (1,8) The activities of enzymes initially present are believed to be responsible for the major chemical changes that occur during the curing of tobacco leaves (3,10). Accordingly, the stability of specific enzymes under curing conditions could markedly influence the final composition of the cured leaf.…”

Section: Discussionmentioning

confidence: 99%

“…Accordingly, the stability of specific enzymes under curing conditions could markedly influence the final composition of the cured leaf. Vickery and Meiss (10) and others (3,4) have shown that the major changes in composition occur during the first 8 to 12 days of air curing. Respiration, which causes a loss of about 16 % of the total organic solids, also ceases by the end of this period (10).…”

Section: Discussionmentioning

confidence: 99%