ISSN:
1573-5036
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary Extracts of snap-bean roots are capable of fixing large amounts of CO2 through carboxylation of phosphoenolpyruvate. Fixation was dependent upon a supply of PEP or substrate capable of being transformed to PEP. 3-PGA served as substrate, but when its conversion to PEP was blocked by fluoride, CO2 fixation was eliminated. Acetate or pyruvate were not effective as substrates. The amount of CO2 fixed was closely associated with production of inorganic phosphorus. From these characteristics and the unfavorable equilibria of the other known carboxylating reactions associated with the Krebs cycle, it is concluded that PEP carboxylase accounts for the major entrance of CO2 into the Krebs cycle. Magnesium stimulated the reaction, while Ca inhibited it. Potassium additions to the assay mixture were found to have no direct effect on stimulation of CO2 fixation. In the presence of NH4, amino acids rather than malate were found to contain the majority of the added CO2. Some implications of the importance of this enzyme system in metabolism of the root and on the soil-root relationship are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01394749
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