Degradation of plastics by microbial enzyme

1. 粪Alcaligenes faecalis T1 PHB解聚酶的聚-3-羟基丁酸（PHB）识别位点：当PHB解聚酶经胰蛋白酶处理后，随着酶分子疏水性的降低，分子量由47 KDa变为42 KDa。与此同时，胰蛋白酶处理的酶失去了phb水解活性，但保持了3-羟基丁酸三聚体水解活性。另一方面，氟磷酸二异丙基处理的酶，既没有PHB水解活性，也没有三聚体水解活性，但对PHB颗粒仍有结合能力。这些结果表明，在PHB解聚合酶中存在识别PHB表面的特定位点。对PHB解聚合酶基因进行了克隆和测序。根据推导出的氨基酸序列，胰蛋白酶可能从酶的c端切割第一个精氨酸。虽然胰蛋白酶释放的5kda片段有可能是一个界面识别位点，但我们认为PHB解聚合酶的界面识别位点是由酶内多肽的若干部分立体组成的。3-羟基丁酸低聚物水解酶基因的克隆：为了比较3-羟基丁酸低聚物水解酶与PHB解聚酶的结构，克隆了3-羟基丁酸低聚物水解酶基因。这项工作正在进行中。PHB解聚合酶对3-羟基丁酸共聚物的降解性：研究了PHB解聚合酶对聚(3-羟基丁酸（3HB)-co-3-羟基戊酸（3HV））和聚（3HB-co-4-羟基丁酸（4HB））的降解性。酶促表面侵蚀速率依次为P(3HB-co- 4hb) P(3HB) P（3HB-co- 3hv）。

1. The Poly-3-hydroxybutyrate (PHB) recognition site of PHB depolymerase of Alcaligenes faecalis T1: When the PHB depolynerase was treated with trypsin, the molecular mass was changed from 47 KDa to 42 KDa in accordance with the decrease of hydrophobicity of the enzyme molecule. At the same time, the trypsintreated enzyme lost PHB-hydrolyzing activity but it maintained 3-hydroxybutyrate trimer-hydrolyzing activity. On the other hand, diisopropylfluorophosphate- treated enzyme, which has neither PHB- nor trimer-hydrolyzing activity, still had the binding capacity to PHB granules. These results indicate that there is a specific site in the PHB depolymerase which recognizes PHB surface. The gene of PHB depolymerase was cloned and sequenced. According to the deduced amino acid sequence, trypsin probably cuts at the first arginine from the C-terminus of the enzyme. Although there is a possibility that the 5 KDa fragment released by trypsin is a interface recognition site, we concluded that the interface recognition site of PHB depolymerase was sterically composed of several portions of peptide in the enzyme.2. Cloning of the gene for 3-hydroxybutyrate oligoner hydrolase: In order to compare the structure of 3-hydroxybutyrate oligomer hydrolase to PHB depolymerase, the gene for the oligoner hydrolase was cloned. This work is under way.3. Degradability of copolymer of 3-hydroxybutyrate by PHB depolymerase: Degradability of poly(3-hydroxybutyric acid (3HB)-co-3-hydroxyvaleric acid (3HV)) and poly(3HB-co-4-hydroxybutyric acid (4HB)) by PHB depolymerase was investigated. The rate of enzymatic surface erosion decreased in the order P(3HB-co-4HB) P(3HB) P(3HB-co-3HV).