Division of Biological Sciences, University of Michigan, 48109, Ann Arbor, Michigan.
J Chem Ecol. 1983 Feb;9(2):285-94. doi: 10.1007/BF00988046.
Tannic acid and quebracho precipitate many times their weight of the abundant leaf protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC). The use of this protein in protein precipitation assays for tannin content is described. Extracts of mature foliage of pin, bur, and black oak precipitate 2.01, 0.69, and 0.09 mg RuBPC/ mg (dry wt) of leaf powder extracted, respectively, at pH 6.1. From these measurements it can be calculated that all three of these oak species have sufficient tannins to precipitate all of the RuBPC present in their foliage. At mildly alkaline pHs, however (pH [Symbol: see text] 7.5), RuBPC is not precipitated by tannins. Since RuBPCis the most abundant protein present in photosynthetic tissues, often constituting as much as 50% of the soluble proteins and 25% of the total proteins in leaf tissue, the interactions of this protein with tannins are highly relevant to an evaluation of the role of tannins as antiherbivore, digestibility-reducing substances. Our measurements provide no basis for arguing that differences in tannin levels in different species reflect differences in the digestibility of leaf proteins or that tannins have any effect whatsoever upon the digestibility of leaf protein under conditions which normally prevail in most insects' guts. These findings emphasize the need to test more of the assumptions underlying contemporary interpretations of the importance of tannins in plant herbivore interactions.
单宁酸和奎拉乔沉淀大量的叶蛋白，核酮糖-1,5-二磷酸羧化酶/加氧酶（RuBPC）。本文描述了将这种蛋白用于测定单宁含量的蛋白沉淀实验。在 pH 值为 6.1 时，从成熟的松树、刺柏和黑橡木叶片中提取的提取物分别沉淀出 2.01、0.69 和 0.09mg RuBPC/mg（干重）的叶粉。根据这些测量结果可以计算出，这三种橡树物种都含有足够的单宁酸来沉淀其叶片中存在的所有 RuBPC。然而，在稍碱性的 pH 值下（pH [符号：见正文]7.5），单宁酸不会沉淀 RuBPC。由于 RuBPC 是光合作用组织中最丰富的蛋白质，通常构成叶片组织中可溶性蛋白的 50%和总蛋白的 25%，因此这种蛋白质与单宁酸的相互作用与单宁酸作为抗食草动物、降低消化率物质的作用密切相关。我们的测量结果并没有为以下观点提供依据，即不同物种中单宁酸水平的差异反映了叶片蛋白消化率的差异，或者单宁酸在大多数昆虫肠道中通常存在的条件下对叶片蛋白消化率有任何影响。这些发现强调了需要对当代解释单宁在植物与食草动物相互作用中的重要性的假设进行更多的检验。
