Pathway of Photosynthetic Malate Formation in Vitis vinifera, a C₃ Plant

Abstract

The time course of intramolecular isotope distribution in phosphoglyceric acid and serine was determined after exposure of grape leaf discs (Vitis vinifera L.) to (8,19,23,24,28), whereas the respective position of this ubiquitous dicarboxylic acid in photosynthetic C3 metabolism remains to be clarified. Based on the observation that isotope distribution in citric acid after assimilation of 14C02 reflected little recycling of oxaloacetate through tricarboxylic acid cycle reactions, a dual anaplerotic function of malic acid by providing both, the C2 and C4 fragments for citrate synthesis, was suggested (16). Apart from this uncertainty concerning the mechanism of malate remetabolization in plants fixing CO2 directly via Calvin cycle reactions, the effective metabolic precursor of malate in the C3 system is controversial also. While pulse-chase experiments with spinach leaf slices gave evidence for a considerable carbon flow from photosynthetic C3 products to malate (3, 4), incongruent labeling patterns of alanine-as a representative of the C3 pathway-and citrate after fixation of 14C02 by Viciafaba were taken as indicative for a 'non-Calvin cycle origin' of the tricarboxylic acid cycle intermediates, including malic acid (13)(14)(15).The present paper reexamines the existence and functioning of a proposed precursor-product relationship between seine and malate in C3 plants (17) by comparative analysis of the labeling patterns of PGA, seine, and malic acid from grape leaf discs after exposure to 14C02 for variable metabolic periods.

Characterization of wines from grape varieties through multivariate statistical analysis of 1H NMR spectroscopic data

“…However, grape variety is a more significant factor affecting malate concentrations of grape (Encarna, Rocio, & Adrian, 2000;Liu et al, 2006;Pereira et al, 2005). Although the relationship between citrate and climatic factors is not clear, some studies have shown that phosphoenolpyruvate carboxykinase (PEPCK) might function in the catabolism of malate and citrate in grape berry (Bahrami, Chen, Walker, Leegood, & Gray, 2001;Ruffner, Brem, & Rast, 1983;Ruffner & Kliewer, 1975). This indicates that the contents of malate and citrate are strongly connected.…”

Non‐photosynthetic Fixation of Carbon Dioxide and Possible Biological Roles in Higher Plants

“…Their data imply a direct derivation of the C1-, moiety of malate from pphosphoglycerate originating in the reductive photosynthetic carbon cycle. Similarly, a metabolic relationship between photosynthetic formation of C,-units arid malate synthesis has been shown for grape leaves (Brem, Ruffner & Rast, 1981;Ruffner, Brem & Rast, 1983). However, carbon flow via a photosynthetic and transitory hexose or starch pool to malate within the leaves cannot be excluded.…”

“…Malate accumulates during early growth followed by its conversion to sugars during ripening. Malic enzyme activity participates in the mobilization of malate during the ripening process of climacteric fruits (Hulme, Jones & Wooltorton, 1963;Dubrey, van Rensburg & Schabort, 1984;Ruffner et al, 1984). Thus, malate accumulates in green berries and falls rapidly after the onset of ripening, concomitant with pronounced increase in sugar concentration due to gluconeogenic metabolism of malate (see Ruffner,I 982).…”

“…The onset of veraison in grape berries embodies the beginning of massive sugar synthesis concomitant with the onset of non-photosynthetically derived malate disappearance suggesting a relationship between the two (see Ruffner, I 982). Evidence for the biochemical pathway of this transformation was sought by administering biogenic malate via [2,3-14C]fumarate for relatively short metabolic periods (6 h), which minimizes randomization of label and the danger of decarboxylation with subsequent refixation of radiocarbon (Ruffner, Koblet & Rast, 1975). The distribution of 14C within glucose from this experiment revealed that the sugar was mainly (80 O/O) labelled in the carbons, I, 2, 5 and 6.…”

The Grape and its Maturation

“…The vine contains the L-(−) malic isomer. The vine assimilates carbon dioxide in the air by a C 3 mechanism (Ruffner et al, 1983). In this manner, during the dark phase of photosynthesis, the leaves and young green grapes fix CO 2 on ribulose 1,5-diphosphate to produce phosphoglyceric acid, which condenses to form hexoses and may also become dehydrated into phosphoenol pyruvic acid.…”