Plant, carbohydrate sucrose metabolism

D. is the primary product of plant photosynthesis, with an annual production 200 x lO mt 95% is further metabolized to other carbohydrates (sucrose, starch, cellulose and others) 5%... 

In addition to enhancement with essential vitamins, amino acids, and proteins, plants can also be metabolically engineered to produce nutritionally superior carbohydrates and lipids. The relative inexpensiveness as well as the capability to grow large-scale quantities make plant production an attractive feature. In the case of carbohydrates such as starch and sucrose, many products or modifications of these products can be produced on a large scale and at much lower costs than are currently available. For example, trehalose, a food additive, was in the past too costly for large-scale production however, it has now been produced in transgenic tobacco tissue at a much reduced cost. 

The neutral and nonspecific FDPases may function in nonphotosynthetic carbohydrate metabolism in higher plants. In the germinating castor bean acetate is utilized for the synthesis of sucrose 107, 108), and the presence of the AMP-sensitive FDPase in plant embryo tissues has been demonstrated by Bianchetti and Satirana 109). The changes in levels of this enzyme in response to changes in physiological conditions 109) support a gluconeogenic role for this enzyme. The role of the nonspecific acid FDPase in plant tissues remains unknown. 

Fructose is found in many plants and is an important portion of dietary carbohydrate. Most commonly it is ingested as free fructose or sucrose. Fructose is not actively transported by the intestinal mucosa, and variable proportions are converted to glucose in the process of absorption in man, about one-sixth is converted (Ml). Most of the metabolism of fructose occurs in the liver. If a renal threshold for fructose exists, it is very low. 

Schrader S. and Sauter J.J. 2002. Seasonal changes of sucrose-phosphate synthase and sucrose synthase activities in poplar wood (Populm x Canadensis Moench robusta) and their possible role in carbohydrate metabolism. J Plant Physiol 159 833-843. 

As already mentioned the most important raw material for the support of mitosis in mammalian tissues appears to be glucose, and there is evidence from observations like those of Brown and Rickless (1949) that sucrose may be equally essential to mitosis in plants. Because of this, and because the actions of all those hormones now known to influence mitosis can be wholly or partly explained in terms of their effects on carbohydrate metabolism, it is appropriate to consider briefly what is now known of the energy requirements of cell division. 

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