Department of Botany, Oregon State University, Corvallis, Oregon.
Plant Physiol. 1966 Oct;41(8):1330-6. doi: 10.1104/pp.41.8.1330.
The relatively high level of fatty acids in soybean nodules and rhizobia from soybean nodules suggested that the glyoxylate cycle might have a role in nodule metabolism. Several species of rhizobia in pure culture were found to have malate synthetase activity when grown on a number of different carbon sources. Significant isocitrate lyase activity was induced when oleate, which presumably may act as an acetyl CoA precursor, was utilized as the principle carbon source. Malate synthetase was active in extracts of rhizobia from nodules of bush bean (Phaseolus vulgaris L.), cowpea (Vigna sinensis L.), lupine (Lupinus angustifolius L.) and soybean (Glycine max L. Merr.). Activity of malate synthetase was, however, barely detectable in rhizobia from alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) and pea (Pisum sativum L.) nodules. Appreciable isocitrate lyase activity was not detected in rhizobia from nodules nor was it induced by depletion of endogenous substrates by incubation of excised bush bean nodules. Although rhizobia has the potential for the formation of the key enzymes of the glyoxylate cycle, the absence of isocitrate lyase activity in bacteria isolated from nodules indicated that the glyoxylate cycle does not operate in the symbiotic growth of rhizobia and that the observed high content of fatty acids in nodules and nodule bacteria probably is related to a structural role.
大豆根瘤和根瘤菌中脂肪酸含量相对较高,表明乙醛酸循环可能在根瘤代谢中起作用。在多种不同碳源上培养时,发现几种纯培养的根瘤菌具有苹果酸合酶活性。当利用油酸作为主要碳源时,会诱导产生显著的异柠檬酸裂解酶活性。油酸可能作为乙酰辅酶 A 的前体起作用。在菜豆(Phaseolus vulgaris L.)、豇豆(Vigna sinensis L.)、羽扇豆(Lupinus angustifolius L.)和大豆(Glycine max L. Merr.)根瘤中的根瘤菌提取物中,苹果酸合酶具有活性。然而,在苜蓿(Medicago sativa L.)、红三叶草(Trifolium pratense L.)和豌豆(Pisum sativum L.)根瘤中的根瘤菌中,苹果酸合酶的活性几乎检测不到。在根瘤中也未检测到异柠檬酸裂解酶活性,并且通过切除菜豆根瘤后耗尽内源性底物也不会诱导其产生。尽管根瘤菌具有形成乙醛酸循环关键酶的潜力,但从根瘤中分离出的细菌缺乏异柠檬酸裂解酶活性表明,乙醛酸循环在根瘤菌的共生生长中不起作用,并且在根瘤和根瘤菌中观察到的高脂肪酸含量可能与结构功能有关。