Saravitz D M, Pharr D M, Carter T E
Department of Horticultural Science, North Carolina State University, Raleigh, North Carolina 27695-7609.
Plant Physiol. 1987 Jan;83(1):185-9. doi: 10.1104/pp.83.1.185.
Galactinol synthase (UDP-galactose:inositol galactosyltransferase) is the first unique enzyme in the biosynthetic pathway of raffinose saccharides. Its role as a regulator of carbon partitioning between sucrose and raffinose saccharides in developing soybean (Glycine max L. Merrill) seeds was examined. Galactinol synthase activity and concentrations of sucrose, stachyose, and raffinose were compared during seed development between two genotypes that were high and two genotypes that were low in mature seed raffinose saccharide concentration. In all genotypes, sucrose concentration increased as seed development progressed, but in both low raffinose saccharide genotypes, greater increases in sucrose concentration were observed late in seed development. Sucrose to stachyose ratios in mature seeds were 2.3-fold greater in low raffinose saccharide genotypes than in the high raffinose saccharide genotypes. During seed development, higher levels of galactinol synthase activity were observed in the high raffinose saccharide genotypes than in the low raffinose saccharide genotypes. A common linear relationship for all four soybean genotypes was shown to exist between galactinol formed estimated from galactinol synthase activity data and the concentration of galactose present in raffinose saccharides. Results of this study implied that galactinol synthase is an important regulator of carbon partitioning between sucrose and raffinose saccharides in developing soybean seeds.
棉子糖合酶（UDP-半乳糖：肌醇半乳糖基转移酶）是棉子糖糖类生物合成途径中的首个独特酶。研究了其在发育中的大豆（Glycine max L. Merrill）种子中作为蔗糖和棉子糖糖类之间碳分配调节剂的作用。在种子发育期间，比较了成熟种子棉子糖糖类浓度高的两种基因型和低的两种基因型之间的棉子糖合酶活性以及蔗糖、水苏糖和棉子糖的浓度。在所有基因型中，随着种子发育的推进，蔗糖浓度增加，但在两种低棉子糖糖类基因型中，在种子发育后期观察到蔗糖浓度有更大幅度的增加。成熟种子中蔗糖与水苏糖的比率，低棉子糖糖类基因型比高棉子糖糖类基因型高2.3倍。在种子发育过程中，高棉子糖糖类基因型中的棉子糖合酶活性水平高于低棉子糖糖类基因型。所有四种大豆基因型的棉子糖合酶活性数据估算的棉子糖生成量与棉子糖糖类中半乳糖浓度之间存在共同的线性关系。本研究结果表明，棉子糖合酶是发育中的大豆种子中蔗糖和棉子糖糖类之间碳分配的重要调节剂。
