A polygalacturonase localized in the Golgi apparatus in Pisum sativum
A polygalacturonase localized in the Golgi apparatus in Pisum sativum
复制标题
豌豆高尔基体中定位的多聚半乳糖醛酸酶
作者：
Ohashi T;Jinno J;Inoue Y;Ito S;Fujiyama K;Ishimizu T
果胶是一种植物细胞壁成分，主要由多聚半乳糖醛酸（PGA）组成，即线性α 1，4-d-半乳糖醛酸（GalUA）骨架。多聚半乳糖醛酸酶（PG）水解PGA中的α 1，4-键。几乎所有的植物PG迄今已确定分泌的可溶性蛋白质。在这里，我们描述了微粒体PG活性豌豆（豌豆）上胚轴和目前的生化证据表明，它是本地化的高尔基体，果胶的生物合成。纯化微粒体PG，并对其进行酶促表征。纯化的酶对具有6个聚合度的吡啶胺化寡聚半乳糖醛酸（PA-GalUA 6）表现出最大活性，PA-GalUA 6的aKm值为11 μM。该酶的底物选择性与PGA合酶的底物选择性互补。用蔗糖密度梯度离心法检测到微粒体中主要的PG活性在高尔基体中。在快速生长的上胚轴中，微粒体PG的活性较低，与PGA合酶的高表达相反。讨论了PG在果胶生物合成或植物生长调节中的作用。
Pectin is a plant cell wall constituent that is mainly composed of polygalacturonic acid (PGA), a linear α1,4-d-galacturonic acid (GalUA) backbone. Polygalacturonase (PG) hydrolyzes the α1,4-linkages in PGA. Nearly all plant PGs identified thus far are secreted as soluble proteins. Here we describe the microsomal PG activity in pea (Pisum sativum) epicotyls and present biochemical evidence that it was localized to the Golgi apparatus, where pectins are biosynthesized. The microsomal PG was purified, and it was enzymatically characterized. The purified enzyme showed maximum activity towards pyridylaminated oligogalacturonic acids with six degrees of polymerization (PA-GalUA6), with aKmvalue of 11 μM for PA-GalUA6. The substrate preference of the enzyme was complementary to that of PGA synthase. The main PG activity in microsomes was detected in the Golgi fraction by sucrose density gradient ultracentrifugation. The activity of the microsomal PG was lower in rapidly growing epicotyls, in contrast to the high expression of PGA synthase. The role of this PG in the regulation of pectin biosynthesis or plant growth is discussed.