Heterologous Expression and Function of Cholesterol Oxidase: A Review.

Cholesterol was first found in gallstones as an animal sterol; hence it is called cholesterol. Cholesterol oxidase is the chief enzyme in the process of cholesterol degradation. Its role is obtained by the coenzyme FAD, which catalyzes the isomerization and oxidation of cholesterol to produce cholesteric 4-ene-3-ketone and hydrogen peroxide at the same time. Recently, a great advance has been made in the discovery of the structure and function of cholesterol oxidase, and it has proven added value in clinical discovery, medical care, food and biopesticides development and other conditions. By recombinant DNA technology, we can insert the gene in the heterologous host. Heterologous expression (HE) is a successful methodology to produce enzymes for function studies and manufacturing applications, where Escherichia coli has been extensively used as a heterologous host because of its economical cultivation, rapid growth, and efficiency in offering exogenous genes. Heterologous expression of cholesterol oxidase has been considered for several microbial sources, such as Rhodococcus equi, Brevibacterium sp., Rhodococcus sp., Streptomyces coelicolor, Burkholderia cepacia ST-200, Chromobacterium, and Streptomyces spp. All related publications of numerous researchers and scholars were searched in ScienceDirect, Scopus, PubMed, and Google Scholar. In this article, the present situation and promotion of heterologous expression of cholesterol oxidase, the role of protease, and the perspective of its possible applications were reviewed.