Division of Environmental Biology, The National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki 305, Japan.
Plant Physiol. 1990 Oct;94(2):781-7. doi: 10.1104/pp.94.2.781.
Effects of MgCl(2) and free fatty acids (FFA) on galactolipid:galactolipid galactosyltransferase (GGGT) and UDP-galactose: 1,2-diacylglycerol galactosyltransferase (UDGT) in chloroplast envelope membranes isolated from spinach (Spinacia oleracea L.) leaves were examined. GGGT activity was sigmoidally stimulated by MgCl(2) with a saturated concentration of more than 5 millimolar. Free alpha-linolenic acid (18:3) caused a drastic increase in GGGT activity under limiting concentrations of MgCl(2), without affecting its maximum activity at higher MgCl(2) concentrations. Free 18:3 alone did not affect the GGGT activity. The effective species of FFA for the stimulation of GGGT activity in the presence of MgCl(2) were unsaturated 16- and 18-carbon fatty acids. GGGT activity was also stimulated by 18:3 in the presence of MnCl(2), CaCl(2) and a high concentration of KCl in place of MgCl(2). UDGT activity was hyperbolically enhanced by MgCl(2) with a saturated concentration of 1 to 2 millimolar. In contrast to GGGT, UDGT was severely inhibited by 18:3, and MgCl(2)-induced stimulation was completely abolished by 18:3. Unsaturated 16- and 18-carbon fatty acids were more inhibitory to UDGT than the saturated acids. The dependence of GGGT activity on monogalactosyldiacylglycerol (MGDG) and MgCl(2) concentrations was identical in the envelope membranes isolated from non- and ozone (0.5 microliter/liter)-fumigated spinach leaves, indicating that GGGT remained active in the leaves during ozone fumigation. The results are discussed in relation to the regulation of galactolipid biosynthesis by the endogenous FFA in the envelopes and to the involvement of GGGT in the triacylglycerol synthesis from MGDG in ozone-fumigated leaves.
研究了从菠菜（Spinacia oleracea L.）叶片中分离的叶绿体被膜中 MgCl2 和游离脂肪酸（FFA）对半乳糖基：半乳糖基二酰基甘油基转移酶（GGGT）和 UDP-半乳糖：1,2-二酰基甘油基半乳糖基转移酶（UDGT）的影响。MgCl2 浓度超过 5 毫摩尔时，GGGT 活性呈 S 形刺激；在 MgCl2 的限制浓度下，游离的α-亚麻酸（18：3）会导致 GGGT 活性急剧增加，而不会影响其在较高 MgCl2 浓度下的最大活性。游离的 18：3 本身并不影响 GGGT 活性。在有 MgCl2 存在的情况下，FFA 刺激 GGGT 活性的有效物质是不饱和的 16 碳和 18 碳脂肪酸。在 MnCl2、CaCl2 和高浓度 KCl 存在的情况下，18：3 也可刺激 GGGT 活性。MgCl2 以 1 至 2 毫摩尔的饱和浓度使 UDGT 活性呈双曲线增强。与 GGGT 不同，UDGT 被 18：3 严重抑制，18：3 完全消除了 MgCl2 诱导的刺激。不饱和 16 碳和 18 碳脂肪酸对 UDGT 的抑制作用强于饱和脂肪酸。在非臭氧（0.5 微升/升）和臭氧熏蒸的菠菜叶片中分离的被膜中，GGGT 活性对单半乳糖二酰基甘油（MGDG）和 MgCl2 浓度的依赖性是相同的，这表明 GGGT 在臭氧熏蒸过程中在叶片中保持活性。结果与被膜中内源性 FFA 对半乳糖脂生物合成的调节以及 GGGT 在臭氧熏蒸叶片中从 MGDG 合成三酰基甘油中的作用有关。
