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Biochemical and Structural Insights into Enzymatic Depolymerization of Polylactic Acid and Other Polyesters by Microbial Carboxylesterases
Biomacromolecules ( IF 5.5 ) Pub Date : 2016-05-02 00:00:00 , DOI: 10.1021/acs.biomac.6b00223 Mahbod Hajighasemi 1 , Boguslaw P. Nocek 2 , Anatoli Tchigvintsev 1 , Greg Brown 1 , Robert Flick 1 , Xiaohui Xu 1 , Hong Cui 1 , Tran Hai 3 , Andrzej Joachimiak 2 , Peter N. Golyshin 3 , Alexei Savchenko 1 , Elizabeth A. Edwards 1 , Alexander F. Yakunin 1
Biomacromolecules ( IF 5.5 ) Pub Date : 2016-05-02 00:00:00 , DOI: 10.1021/acs.biomac.6b00223 Mahbod Hajighasemi 1 , Boguslaw P. Nocek 2 , Anatoli Tchigvintsev 1 , Greg Brown 1 , Robert Flick 1 , Xiaohui Xu 1 , Hong Cui 1 , Tran Hai 3 , Andrzej Joachimiak 2 , Peter N. Golyshin 3 , Alexei Savchenko 1 , Elizabeth A. Edwards 1 , Alexander F. Yakunin 1
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Polylactic acid (PLA) is a biodegradable polyester derived from renewable resources, which is a leading candidate for the replacement of traditional petroleum-based polymers. Since the global production of PLA is quickly growing, there is an urgent need for the development of efficient recycling technologies, which will produce lactic acid instead of CO2 as the final product. After screening 90 purified microbial α/β-hydrolases, we identified hydrolytic activity against emulsified PLA in two uncharacterized proteins, ABO2449 from Alcanivorax borkumensis and RPA1511 from Rhodopseudomonas palustris. Both enzymes were also active against emulsified polycaprolactone and other polyesters as well as against soluble α-naphthyl and p-nitrophenyl monoesters. In addition, both ABO2449 and RPA1511 catalyzed complete or extensive hydrolysis of solid PLA with the production of lactic acid monomers, dimers, and larger oligomers as products. The crystal structure of RPA1511 was determined at 2.2 Å resolution and revealed a classical α/β-hydrolase fold with a wide-open active site containing a molecule of polyethylene glycol bound near the catalytic triad Ser114-His270-Asp242. Site-directed mutagenesis of both proteins demonstrated that the catalytic triad residues are important for the hydrolysis of both monoester and polyester substrates. We also identified several residues in RPA1511 (Gln172, Leu212, Met215, Trp218, and Leu220) and ABO2449 (Phe38 and Leu152), which were not essential for activity against soluble monoesters but were found to be critical for the hydrolysis of PLA. Our results indicate that microbial carboxyl esterases can efficiently hydrolyze various polyesters making them attractive biocatalysts for plastics depolymerization and recycling.
中文翻译：
生化和结构上的洞察力通过微生物羧酯酶酶解聚乳酸和其他聚酯。
聚乳酸（PLA）是可再生资源衍生的可生物降解的聚酯，是替代传统石油基聚合物的领先候选者。由于PLA的全球产量正在快速增长，因此迫切需要开发高效的回收技术，该技术将最终生成乳酸而不是CO 2。在筛选了90种纯化的微生物α/β-水解酶后，我们在两种未表征的蛋白中鉴定了对乳化PLA的水解活性，这两种蛋白分别是来自Bocanumensis的ABO2449和来自Phodopseudomonas palustris的RPA1511 。两种酶也对乳化聚己内酯和其它聚酯以及针对可溶性α萘基和活性p-硝基苯基单酯。此外，ABO2449和RPA1511都催化固体PLA的完全或广泛水解，产生乳酸单体，二聚体和较大的低聚物。RPA1511的晶体结构以2.2Å的分辨率测定，显示出经典的α/β水解酶折叠，带有一个宽开放的活性位点，该活性位点包含一个结合在催化三联体Ser114-His270-Asp242附近的聚乙二醇分子。两种蛋白质的定点诱变表明催化三联体残基对于单酯和聚酯底物的水解都很重要。我们还确定了RPA1511（Gln172，Leu212，Met215，Trp218和Leu220）和ABO2449（Phe38和Leu152）中的几个残基，这些残基对于抗可溶性单酯不是必需的，但发现对PLA的水解至关重要。
更新日期：2016-05-02
中文翻译：
生化和结构上的洞察力通过微生物羧酯酶酶解聚乳酸和其他聚酯。
聚乳酸（PLA）是可再生资源衍生的可生物降解的聚酯，是替代传统石油基聚合物的领先候选者。由于PLA的全球产量正在快速增长，因此迫切需要开发高效的回收技术，该技术将最终生成乳酸而不是CO 2。在筛选了90种纯化的微生物α/β-水解酶后，我们在两种未表征的蛋白中鉴定了对乳化PLA的水解活性，这两种蛋白分别是来自Bocanumensis的ABO2449和来自Phodopseudomonas palustris的RPA1511 。两种酶也对乳化聚己内酯和其它聚酯以及针对可溶性α萘基和活性p-硝基苯基单酯。此外，ABO2449和RPA1511都催化固体PLA的完全或广泛水解，产生乳酸单体，二聚体和较大的低聚物。RPA1511的晶体结构以2.2Å的分辨率测定，显示出经典的α/β水解酶折叠，带有一个宽开放的活性位点，该活性位点包含一个结合在催化三联体Ser114-His270-Asp242附近的聚乙二醇分子。两种蛋白质的定点诱变表明催化三联体残基对于单酯和聚酯底物的水解都很重要。我们还确定了RPA1511（Gln172，Leu212，Met215，Trp218和Leu220）和ABO2449（Phe38和Leu152）中的几个残基，这些残基对于抗可溶性单酯不是必需的，但发现对PLA的水解至关重要。
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