Enzyme—metal hybrid catalysts bridge the gap between enzymatic and heterogeneous catalysis, which is significant for expanding biocatalysis to a broader scope. Previous studies have demonstrated that the enzyme—metal hybrid catalysts exhibited considerably higher catalytic efficiency in cascade reactions, compared with that of the combination of separated enzyme and metal catalysts. However, the precise mechanism of this phenomenon remains unclear. Here, we investigated the diffusion process in enzyme—metal hybrid catalysts using Pd/lipase-Pluronic conjugates and the combination of immobilized lipase (Novozyme 435) and Pd/C as models. With reference to experimental data in previous studies, the Weisz—Prater parameter and efficiency factor of internal diffusion were calculated to evaluate the internal diffusion limitations in these catalysts. Thereafter, a kinetic model was developed and fitted to describe the proximity effect in hybrid catalysts. Results indicated that the enhanced catalytic efficiency of hybrid catalysts may arise from the decreased internal diffusion limitation, size effect of Pd clusters and proximity of the enzyme and metal active sites, which provides a theoretical foundation for the rational design of enzyme-metal hybrid catalysts.

酶-金属杂化催化剂弥合了酶催化和非均相催化之间的差距，这对于将生物催化扩展到更广泛的范围具有重要意义。先前的研究表明，与分离的酶和金属催化剂的组合相比，酶-金属杂化催化剂在级联反应中表现出更高的催化效率。然而，这种现象的确切机制仍不清楚。在这里，我们使用 Pd/脂肪酶-Pluronic 偶联物以及固定化脂肪酶 (Novozyme 435) 和 Pd/C 的组合作为模型研究了酶-金属杂化催化剂中的扩散过程。参考以往研究中的实验数据，计算了内扩散的 Weisz-Prater 参数和效率因子，以评估这些催化剂的内扩散限制。此后，开发并拟合了一个动力学模型来描述混合催化剂中的邻近效应。结果表明，杂化催化剂的催化效率提高可能源于内部扩散限制的降低、Pd簇的尺寸效应以及酶与金属活性位点的接近，这为酶-金属杂化催化剂的合理设计提供了理论基础。