Redirecting Photosynthetic Reducing Power into Light-Driven Biosynthesis of Bioactive Natural Compounds

Plants can synthesize around 200,000 different specialized metabolites, many of which are of commercial interest as they can be utilized as pharmaceuticals. Often these compounds are produced at low levels in the plants, and due to their complex structures, chemical synthesis is not feasible. The cytochrome P450s (P450s) are among the enzymes that participate in the biosynthesis of these compounds.

We are aiming at coupling photosynthetic electron transport directly to a metabolon of P450s to develop a system in which the electrons derived from water can be used directly in the reactions of the P450s. As a model system we are working with the enzymes producing the cyanogenic glucoside dhurrin in the endoplasmic reticulum membranes of Sorghum bicolor. Three enzymes are involved in dhurrin biosynthesis, two P450s (CYP79A1 and CYP71E1) and a glycosyl transferase, UGT85B1. Recently, we have found that these enzymes can be expressed in the chloroplasts of Nicotiana benthamiana, where they show light-dependent dhurrin production with the P450s driven by electrons delivered from photosystem I (PSI) by ferredoxin [1].

In this project we have genetically fused the catalytic domain of CYP79A1 to a PSI subunit in Synechococcus sp. PCC 7002, thereby making it an integral part of PSI to facilitate efficient electron transfer. Preliminary results indicate that the PSI-P450 fusion is active both in isolated thylakoids and in living cyanobacteria. It is envisioned that the PSI-P450 system can be developed as a light-driven and environmentally friendly production system of bioactive compounds relevant to the pharmaceutical or chemical industries.

References:

[1] Nielsen, A. Z. et al. Redirecting Photosynthetic Reducing Power toward Bioactive Natural Product Synthesis. ACS Synth. Biol., 2013, 2 (6), pp 308–315, DOI: 10.1021/sb300128r

Funding from UNIK Center for Synthetic Biology, Interdisciplinary Research Center “bioSYNergy” and the VILLUM Research Center “Plant Plasticity” is gratefully acknowledged.