This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: fagopyritol A1 biosynthesis
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Sugar Derivatives Biosynthesis|
|Degradation/Utilization/Assimilation → Secondary Metabolites Degradation → Sugar Derivatives Degradation → Cyclitols Degradation|
Some taxa known to possess this pathway include : Fagopyrum esculentum
Expected Taxonomic Range: Caryophyllales
Fagopyritols are galactosyl cyclitols found primarily in seeds of buckwheat (Fagopyrum esculentum). Whereas maturing embryos of many plant seeds accumulate raffinose, stachyose and verbascose (in addition to sucrose) as the predominant soluble sugars, maturing embryos of buckwheat seeds accumulate fagopyritols. These compounds are grouped into two main series: A and B, which differ from the positioning of the O-α-D-galactopyranosyl linkage to 1D-chiro-inositol [(1->3) for A series, (1->2) for B series]. The first fagopyritol of the A series is termed fagopyritol A1. The subsequent di- and tri-galactopyranosyl-fagopyritols (A2 and A3) result from the addition of galactosyl units linked in (1->6)-O-α-D-galactopyranosyl to fagopyritol A1. Fagopyritols of the A series have only been detected so far in the seeds of bluckwheat [Horbowicz05, Steadman01] whereas fagopyritols of the B series have been detected in several other species (mostly fagopyritol B1). Fagopyritols have attracted attention as they are structurally similar to a galactosamine derivative of D-chiro-inositol, a putative insulin mediator, and may be useful in the treatment of non-insulin-dependent diabetes mellitus and polycystic ovary syndrome (for references, see the introduction of [Obendorf00]).
Key Notes on the enzymes: Crude extracts from immature embryos harvested 20 days after pollination or from buckwheat bran prepared from mature dry seeds did not show any fagopyritol synthase activity using galactinol as galactosyl donor. The same experiments was successful in producing fagopyritol B1 using UDP-galactose instead of galactinol, suggesting that fagopyritol synthases might be homologous to galactinol synthases (GolS). Using conserved oligonucleotide sequences of GolS, two fagopyritol synthases genes (GolS-1 and GolS-2) were identified from cDNA libraries of buckwheat developing seeds harvested 2025 days after pollination. The enzymes catalyze the formation of fagopyritol A1 and B1 but not the subsequent compounds in the series [Ueda05]. To date no enzyme has been identified that can catalyze the formation of fagopyritols A2, B2, A3 or B3.
Obendorf00: Obendorf RL, Steadman KJ, Fuller DJ, Horbowicz M, Lewis BA (2000). "Molecular structure of fagopyritol A1 (O-alpha-D-galactopyranosyl-(1 --> 3)-D-chiro-inositol) by NMR." Carbohydr Res 328(4);623-7. PMID: 11093720
Steadman01: Steadman KJ, Fuller DJ, Obendorf RL (2001). "Purification and molecular structure of two digalactosyl D-chiro-inositols and two trigalactosyl D-chiro-inositols from buckwheat seeds." Carbohydr Res 331(1);19-25. PMID: 11284502
Ueda05: Ueda, T., Coseo, M.P., Harrell, T.J., Obendorf, R.L. (2005). "A multifunctional galactinol synthase catalyzes the synthesis of fagopyritol A1 and fagopyritol B1 in buckwheat seed." Plant Science 168:681-690.
Iuorno: Iuorno MJ, Jakubowicz DJ, Baillargeon JP, Dillon P, Gunn RD, Allan G, Nestler JE "Effects of d-chiro-inositol in lean women with the polycystic ovary syndrome." Endocr Pract 8(6);417-23. PMID: 15251831
Kennington90: Kennington AS, Hill CR, Craig J, Bogardus C, Raz I, Ortmeyer HK, Hansen BC, Romero G, Larner J (1990). "Low urinary chiro-inositol excretion in non-insulin-dependent diabetes mellitus." N Engl J Med 323(6);373-8. PMID: 2370888
Larner88: Larner J, Huang LC, Schwartz CF, Oswald AS, Shen TY, Kinter M, Tang GZ, Zeller K (1988). "Rat liver insulin mediator which stimulates pyruvate dehydrogenase phosphate contains galactosamine and D-chiroinositol." Biochem Biophys Res Commun 151(3);1416-26. PMID: 2833261
Larner89: Larner J, Huang LC, Suzuki S, Tang G, Zhang C, Schwartz CF, Romero G, Luttrell L, Kennington AS (1989). "Insulin mediators and the control of pyruvate dehydrogenase complex." Ann N Y Acad Sci 573;297-305. PMID: 2517463
Niwa83: Niwa T, Yamamoto N, Maeda K, Yamada K, Ohki T, Mori M (1983). "Gas chromatographic--mass spectrometric analysis of polyols in urine and serum of uremic patients. Identification of new deoxyalditols and inositol isomers." J Chromatogr 277;25-39. PMID: 6643610
Yoshida06: Yoshida K, Yamaguchi M, Morinaga T, Ikeuchi M, Kinehara M, Ashida H (2006). "Genetic modification of Bacillus subtilis for production of D-chiro-inositol, an investigational drug candidate for treatment of type 2 diabetes and polycystic ovary syndrome." Appl Environ Microbiol 72(2);1310-5. PMID: 16461681
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