Galacturonate metabolism

Moreover, we have shown that the SCPP strain is able to metabolize galacturonic acid... 

Loewus, F.A., and Kelly, S., 1961. The metabolism of D-galacturonic acid and its methyl ester in the detached ripening strawberry. Arch. Biochem. Biophys. 95 483 193. 

Most of the acids of the metabolism are found in trace amounts in ripe grape pulp (pyruvic, a-ketoglutaric, fumaric, galacturonic, shikimic, etc.). Must acidity, an important element of enological data, is essentially constituted by three acids tartaric, malic and citric acid (Volume 2, Section 1.2.2). It can vary from 3 to 10 g/1 in sulfuric acid or from 4.5 to 15 g/1 in tartaric acid, depending on the cultivar, the climate and grape maturity. Phosphoric acid is the preponderant inorganic anion. 

We also lack any knowledge of the ultimate fate of pectic substances and galacturonic add in plant tissues. Little proof exists whether pectic substances may or may not serve as reserve carbohydrates that can be metabolized by the cell. From the fragmentary information on hand, it is not even certain that these pol mronides, once formed, actually disappear from the tissue. The decreasing proportion of pectin in a tissue can be often explained by dilution with newly formed constituents and higher proportion of waterSuch retention of the pectic polyuronides by the tissue would be in harmony with their known structural function. 

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