Intracellular degradation of poly(3-hydroxybutyrate) (PHB) in bacteria is not yet clear. The properties of the autodigestion of native PHB granules from Zoogloea ramigera I-16-M were examined. The release of D(-)-3-hydroxybutyrate was observed only at pH values higher than about 8.5 and at relatively high ionic strength (optimal concentration 200 mM NaCl). Triton X-100 and diisopropylfluorophosphate inhibited this reaction. Addition of the supernatant fraction of Z. ramigera did not increase the release of D(-)-3-hydroxybutyrate from the native PHB granules. On the other hand, using the protease-treated PHB granules from Alcaligenes eutrophus as a substrate, PHB depolymerase activity was detected in the supernatant fraction of Z. ramigera cells. The soluble PHB depolymerase showed similar properties to the enzyme in the PHB granules. Since PHB depolymerase activity was found in fractions containing D(-)-3-hydroxybutyrate oligomer hydrolase activity, which were separated by DEAE-Toyopearl or by Sephacryl S-100, it is possible that the intracellular PHB depolymerase is identical to the oligomer hydrolase which has been purified already.

中文翻译：

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圆球菌I-16-M的聚（3-羟基丁酸酯）颗粒的细胞内降解。

细菌中的聚（3-羟基丁酸酯）（PHB）的细胞内降解尚不清楚。检查了来自半球形动物I-16-M的天然PHB颗粒的自动消化特性。仅在高于约8.5的pH值和相对高的离子强度（最佳浓度200 mM NaCl）下观察到D（-）-3-羟基丁酸酯的释放。Triton X-100和氟磷酸二异丙酯抑制了该反应。添加雷曼氏梭菌的上清液级分不会增加天然PHB颗粒中D（-）-3-羟基丁酸酯的释放。另一方面，使用来自真生产碱杆菌（Alcaligenes eutrophus）的经蛋白酶处理的PHB颗粒作为底物，在Ramigera Z. ramigera细胞的上清液部分中检测到PHB解聚酶活性。可溶性PHB解聚酶的性质与PHB颗粒中的酶相似。