Degradation of plastics by microbial enzyme

1.粪产碱菌PHB解聚酶的聚-3-羟基丁酸酯(PHB)识别位点：用胰酶处理PHB解聚酶时，随着酶分子疏水性的降低，PHB解聚酶的相对分子质量从47 KDa变为42 KDa。同时，经胰酶处理的酶失去了对PHB的水解性，但保持了对3-羟基丁酸酯三聚体的水解性。另一方面，二异丙基氟磷酸盐处理的酶既不具有PHB-水解性，也不具有三聚体水解性，仍具有与PHB颗粒的结合能力。这些结果表明，在PHB解聚酶中有一个识别PHB表面的特定位点。对PHB解聚酶基因进行了克隆和测序。根据推导的氨基酸序列，胰酶可能从酶的C末端第一个精氨酸开始切割。尽管存在胰酶释放的5 KDa片段是界面识别位点的可能性，但我们得出结论：PHB解聚酶的界面识别位点是由酶中几个部分的多肽立体组成的。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和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解聚对3-羟基丁酸酯共聚物的降解性：研究了聚3-羟基丁酸(3HB)-3-羟基戊酸(3HV)和聚(3HB-co-4-羟基丁酸(4HB))的PHB解聚降解性。酶的表面腐蚀率按P(3HB-co-4HB)P(3HB)P(3HB-co-3HV)顺序递减。

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).