Glucuronic acid, from inositol

The role, if any, of L-glucuronic acid in the metabolism of myo-inositol in vivo is unknown, since this acid has not been found in Nature nor been used in metabolic studies. Apparently, however, the d and l enantiomorphs of glucuronic acid are formed from myoinositol by separate enzymes.131... 

Figure 1. Inositol synthesis and catabolism. Inositol is synthesized from glucose-6-phosphate (Glucose 6-P) by the action of L-wyo-inositol 1-phosphate synthase (MIPS) and wyo-inositol monophosphatase (IMP). IMPase is also required for the last step of inositol (1,4,5)P3 second messenger breakdown. The first step in inositol catabolism utilizes the wyo-inositol oxygenase (MIOX) enzyme, which cleaves the inositol ring to form D-glucuronic acid.

From the above degradation products, a myo-inositol-D-glucuronic acid-2-amino-2-deoxy-D-glucose has been isolated crystalline it seems to be a common unit in the molecule of the phytoglycosphingolipids of all seeds.130... 

Considering the fact that an enzyme in rat kidney preparations readily converted myo-inosltol to glucuronic acid (Charalampous and Lyras, 1957), attempts were made (Burns et al., 1956) to demonstrate the formation of L-AA in plants and animals from labelled myo-inositol. However, Loewus et al. (1962) completely ruled out the possibility of myoinositol serving as an Important precursor of L-AA. 

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