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Plant Physiology 56:67-71 (1975) © 1975 American Society of Plant Biologists Phosphoenolpyruvate Carboxykinase Activity in Grape Berries 1a Department of Viticulture and Enology, University of California, Davis, California 95616
Phosphoenolpyruvate (PEP) carboxykinase activity was found in crude extracts of `Pinot noir' grape berries. The enzyme required ATP, Mn2+ plus Mg2+, a pH of 6.6, and a temperature of 40 C for maximum activity. The range in concentration of oxaloacetic acid needed for maximum phosphoenolpyruvate carboxykinase activity was 5 to 10 mM, and the Km for HCO3- in the exchange of 14CO2 into oxaloacetic acid was 26.8 mM. Changes in the activity of PEP carboxykinase and PEP carboxylase in berries were studied at weekly intervals throughout fruit development. PEP carboxykinase had maximum activity 4 weeks after flowering, and during the following 11 weeks remained relatively constant. The activity of PEP carboxylase was 2- to 4-fold higher than PEP carboxykinase throughout fruit development, and changed little except for a sharp reduction at the onset of ripening.
1 This research was supported in part by a fellowship grant to H.P.R. from the Swiss National Foundation and by a grant from the California Wine Advisory Board. This article has been cited by other articles:
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