ISHS Acta Horticulturae 139: Fruit Set and Development, XXI IHC
REGULATION OF MALIC ACID METABOLISM IN BERRIES OF VITIS VINIFERA |
| Authors: | D. Possner, H.P. Ruffner, D.M. Rast |
| Abstract:
Based on tracer experiments with sucrose-U-14C, administered to grape berries before and after the onset of ripening, it is concluded that the decrease in malic acid during maturation is the result of reduced malate synthesis in combination with an accelerated catabolic rate. As might be expected from the available physiological data, which generally favour a decarboxylative action of malic enzyme (ME; EC 1.1.1.40) in fruit ripening, no negative correlation between areas of high enzymic activity and malate concentration was detectable in green berries, while in the maturing fruit the zone of highest ME activity also had the lowest malic acid levels. The physiological potential of certain in vitro properties of grape ME, such as the interrelationship between pH and enzymic affinity for malate, as well as the inhibitory effect of high NADPH proportions on malic acid decarboxylation, are discussed. | |
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