Department of Botany and Plant Sciences, University of California, Riverside, California 92521.
Plant Physiol. 1986 Jun;81(2):464-70. doi: 10.1104/pp.81.2.464.
The [(14)C] moiety from [(3)H]UDP[(14)C]glucose was incorporated by intact cotton fibers into hot water soluble, acetic-nitric reagent soluble and insoluble components, and chloroform-methanol soluble lipids; the [(3)H] UDP moiety was not incorporated. The (3)H-label can be exchanged rapidly with unlabeled substrate in a chase experiment. The cell wall apparent free space of cotton fibers was in the order of 30 picomoles per milligram of dry fibers; 25 picomoles per milligram easily exchanged and about 5 picomoles per milligram more tightly adsorbed. At 50 micromolar UDPglucose, 70% of the [(14)C]glucose was found in the lipid fraction after both a short labeling period and chase. The percent of [(14)C]glucose incorporated into total glucan increased slightly with chase, but the fraction of total glucans incorporated into insoluble acetic-nitric reagent (cellulose) did increase within a 30-minute chase period. The data supports the concept that glucan synthesis, including cellulose, as well as the synthesis of steryl glucosides, acetylated steryl glucosides, and glucosyl-phosphoryl-polyprenol from externally supplied UDPglucose occurs at the plasma membrane-cell wall interface. The synthase enzymes for such synthesis must be part of this interfacial membrane system.
[(14)C] 部分从 [(3)H]UDP[(14)C]葡萄糖被完整的棉纤维掺入热水可溶性、乙酸-硝酸试剂可溶性和不溶性成分，以及氯仿-甲醇可溶性脂质；[(3)H]UDP 部分未掺入。在追踪实验中，(3)H 标记可以与未标记的底物快速交换。棉纤维的细胞壁表观游离空间的顺序为每毫克干燥纤维 30 皮摩尔；25 皮摩尔容易交换，大约 5 皮摩尔更紧密吸附。在 50 微摩尔 UDPglucose 下，短标记期和追踪后，[(14)C]葡萄糖的 70%发现存在于脂质部分。随着追踪，[(14)C]葡萄糖掺入总葡聚糖的百分比略有增加，但总葡聚糖中掺入不溶性乙酸-硝酸试剂（纤维素）的部分在 30 分钟的追踪期内确实增加。这些数据支持这样的概念，即包括纤维素在内的葡聚糖合成，以及甾醇葡萄糖苷、乙酰化甾醇葡萄糖苷和葡萄糖基磷酸多萜醇从外部供应的 UDPglucose 的合成，发生在质膜-细胞壁界面。这种合成的合成酶必须是这个界面膜系统的一部分。
