Wong P P, Evans H J
Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331.
Plant Physiol. 1971 Jun;47(6):750-5. doi: 10.1104/pp.47.6.750.
Soybean (Glycine max) nodule bacteroids contain high concentrations of poly-beta-hydroxybutyrate and possess a depolymerase system that catalyzes the hydrolysis of the polymer. Changes in poly-beta-hydroxybutyrate content and in activities of nitrogenase, beta-hydroxybutyrate dehydrogenase, and isocitrate lyase in nodule bacteroids were investigated under conditions in which the supply of carbohydrate from the soybean plants was interrupted. The poly-beta-hydroxybutyrate content of bacteroids did not decrease appreciably until the carbohydrate supply from the host plants was limited by incubation of excised nodules, incubation of plants in the dark, or by senescence of the host plant. Isocitrate lyase activity in bacteroids was not detected until poly-beta-hydroxybutyrate utilization appeared to begin. The presence of a supply of poly-beta-hydroxybutyrate in nodule bacteroids was not sufficient for maintenance of high nitrogenase activity under conditions of limited carbohydrate supply from the host plant. An unusually high activity of beta-hydroxybutyrate dehydrogenase was observed in bacteroid extracts but no significant change in the activity of this enzyme was observed as a result of apparent utilization of poly-beta-hydroxybutyrate by nodule bacteroids.
大豆（Glycine max）根瘤类菌体含有高浓度的聚-β-羟基丁酸酯，并拥有一个催化该聚合物水解的解聚酶系统。在大豆植株碳水化合物供应中断的条件下，研究了根瘤类菌体中聚-β-羟基丁酸酯含量以及固氮酶、β-羟基丁酸脱氢酶和异柠檬酸裂解酶活性的变化。直到通过切除根瘤进行培养、将植株置于黑暗中培养或宿主植物衰老导致宿主植物碳水化合物供应受到限制时，类菌体中的聚-β-羟基丁酸酯含量才会明显下降。直到聚-β-羟基丁酸酯利用似乎开始时，才检测到类菌体中的异柠檬酸裂解酶活性。在宿主植物碳水化合物供应有限的条件下，根瘤类菌体中存在聚-β-羟基丁酸酯供应不足以维持高固氮酶活性。在类菌体提取物中观察到β-羟基丁酸脱氢酶活性异常高，但由于根瘤类菌体明显利用聚-β-羟基丁酸酯，该酶的活性未观察到显著变化。
