Cytrochrome P450 (CYP) is a potential candidate for detoxification of environmental contaminants owing to its wide detoxification capacity. Unfortunately, its complex catalytic systems have posed great challenges to the realization of their in vitro applications. Additionally, P450 enzymes are unstable outside their hosts and can be easily denatured. Thermostable CYP119 have recently proved to be useful models in studying industrial catalytic applications of P450 which, however, require thorough understanding of the inherent coenzymes for CYP119 catalysis. Previously conducted research shown that oxidation of CYP119 under light irradiation results in compound 1, a key intermediate in the catalytic pathway. Consequently, semiconductors such as TiO2 can be used as support enzymes as they can be effectively applied in catalytic activities involving simultaneous oxidation and reduction reactions. Metal oxides such as CeO2 have been coupled with pure TiO2 to improve its performance in catalytic systems.
In a recent study published in the Chemical Engineering Journal, Nanchang Hangkong University researchers: Professor Hualin Jiang, Xueqin Li, Menglin Li, Pingping Niu, Tao Wang, Dezhi Chen, Professor Pinghua Chen and Professor Jian-Ping Zou studied the photocatalytic property of a Cytrochrome P450 119 coupled with a semiconductor composite of CeO2-3TiO2. TiO2 particularly exhibits good biocompatibility, non-toxicity and is generally cost-effective. The high toxicity enabled reduction of Cr (VI) thus allowing investigation of the catalytic activity and mechanism of the coupled system. The samples were characterized using numerous methods including elemental mapping and X-ray diffraction. The main objective was to further understanding of the catalytic pathway of CYP enzymes.
Reduction of Cr (VI) was performed under light irradiation, first using bare CYP119 enzymes and secondly using bare CYP119 enzyme coupled with a semiconductor and the two resulted compared. As anticipated, bare CYP119 could not reduce Cr (VI) under light irradiation. However, semiconductor coupled system exhibited high photocatalytic reactivity, higher than that of CYP119 and CeO2-TiO2. On the other hand, according to the photocatalytic mechanism analysis, the authors noted that both the enzyme and the semiconductor were synergistic to the function in the coupled system.
It was worth noting that CYP119 enzymes could not directly use the light energy. Instead, it required oxidized active species, generated by the semiconductor under light irradiation, to be activated.
In a nutshell, the study is the first to construct a CYP-semiconductor coupled system and trigger photocatalytic reactivity. The semiconductor plays a significant role in generating oxidized active species under light irradiation to activate the enzyme for catalyzing the substrates. Unlike the classical catalytic systems, the photocatalytic system is generally cost-effective and more convenient. In a statement to Advances in Engineering, Professor Hualin Jiang observed that the study has showcased the underlying potential of harvesting light energy using P450 enzymes, which is important for both its theoretical and practical research and related applications.
Jiang, H., Li, X., Li, M., Niu, P., Wang, T., Chen, D., Chen, P., & Zhou, J. (2019). A new strategy for triggering photocatalytic activity of Cytrochrome P450 by coupling of semiconductors. Chemical Engineering Journal, 358, 58-66.