Sluggish surface reaction is a critical factor that strongly governs the efficiency of photocatalytic solar fuel production, particularly in CO2-to-ethanol photoconversion. Here, inspired by the principles underlying enzyme catalytic proficiency and specificity, we report a biomimetic photocatalyst that affords superior CO2-to-ethanol photoreduction efficiency (5.5 millimoles gram−1 hour−1 in average with 98.2% selectivity) distinctly surpassing the state of the art. The key is to create a class of catalytic pocket, which contains spatially organized NH2…Cu-Se(-Zn) multiple functionalities at close range, over ZnSe colloidal quantum wells. Such structure offers a platform to mimic the concerted cooperation between the active site and surrounding secondary/outer coordination spheres in enzyme catalysis. This is manifested by the chemical adsorption and activation of CO2 via a bent geometry, favorable stabilization toward a variety of important intermediates, promotion of multielectron/proton transfer processes, etc. These results highlight the potential of incorporating enzyme-like features into the design of photocatalysts to overcome the challenges in CO2 reduction.
Shaohua Guo,Jinxin Xu,Ioannis V. Pavlidis,Dongming Lan,Uwe T. Bornscheuer,Jinsong Liu,Yonghua Wang
Monoacylglycerol and diacylglycerol lipases are industrially interesting enzymes, due to the health benefits that arise from the consumption of diglycerides compared to the traditional triglyceride oils. Most lipases possess an α-helix (lid) directly over the catalytic pocket which regulates the activity of the enzyme. Generally, lipases exist in active and inactive conformations, depending on the positioning of this lid subdomain. However, lipase SMG1, a monoacylglycerol and diacylglycerol specific lipase, has an atypical activation mechanism. In the present study we were able to prove by crystallography, in silico analysis and activity tests that only two positions, residues 102 and 278, are responsible for a gating mechanism that regulates the active and inactive states of the lipase, and that no significant structural changes take place during activation except for oxyanion hole formation. The elucidation of the gating effect provided data enabling the rational design of improved lipases with 6-fold increase in the hydrolytic activity toward diacylglycerols, just by providing additional substrate stabilization with a single mutation (F278N or F278T). Due to the conservation of F278 among the monoacylglycerol and diacylglycerol lipases in the Rhizomucor miehei lipase-like family, the gating mechanism described herein might represent a general mechanism applicable to other monoacylglycerol and diacylglycerol lipases as well. Database Structural data are available in the Protein Data Bank under the accession numbers 4ZRE (F278D mutant) and 4ZRD (F278N mutant).
Shijin Wu,Qiang Wang,Xiaojing Ma,Lequan Qiu,Hongde Yan
The amino acid residues at the entrance of the catalytic pocket may impose steric hindrance on the substrate to enter the active center of the enzyme. Based on the analysis of the three-dimensional structure of the Saccharomyces cerevisiae old yellow enzyme 3 (OYE3), four bulky residues were chosen and mutated to small amino acids. The results showed that mutation of the W116 residue had interesting impacts on the catalytic performance. All four variants became inactive for the reduction of ( R )-carvone and ( S )-carvone, but inverted the stereoselectivity for the reduction of ( E / Z )-citral. The mutation of the F250 residue had a more positive effect on the activity and stereoselectivity. Two variants, F250A and F250S, showed excellent diastereoselectivity and activity for the reduction of ( R )-carvone (de > 99%, c > 99%) and increased diastereoselectivity and activity for the reduction of ( S )-carvone (de > 96%, c > 80%). One variant of the P295 residue, P295G, displayed excellent diastereoselectivity and activity only for the reduction of ( R )-carvone (de > 99%, c > 99%). Mutation of the Y375 residue had a negative impact on the activity of the enzyme. These findings provide some solutions for rational enzyme engineering of OYE3.
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