*Review* **Multifunctional Enzymes in Microbial Secondary Metabolic Processes**

**Jun-Tao Wang, Ting-Ting Shi, Lin Ding, Juan Xie and Pei-Ji Zhao \***

State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, School of Life Sciences, Yunnan University, Kunming 650091, China

**\*** Correspondence: pjzhao@ynu.edu.cn

**Abstract:** Microorganisms possess a strong capacity for secondary metabolite synthesis, which is represented by tightly controlled networks. The absence of any enzymes leads to a change in the original metabolic pathway, with a decrease in or even elimination of a synthetic product, which is not permissible under conditions of normal life activities of microorganisms. In order to improve the efficiency of secondary metabolism, organisms have evolved multifunctional enzymes (MFEs) that can catalyze two or more kinds of reactions via multiple active sites. However, instead of interfering, the multifunctional catalytic properties of MFEs facilitate the biosynthetic process. Among the numerous MFEs considered of vital importance in the life activities of living organisms are the synthases involved in assembling the backbone of compounds using different substrates and modifying enzymes that confer the final activity of compounds. In this paper, we review MFEs in terms of both synthetic and post-modifying enzymes involved in secondary metabolic biosynthesis, focusing on polyketides, non-ribosomal peptides, terpenoids, and a wide range of cytochrome P450s(CYP450s), and provide an overview and describe the recent progress in the research on MFEs.

**Keywords:** multifunctional enzymes; secondary metabolic; synthases; post-modifying enzymes
