Harnessing Photosynthetic ATP for Whole-Cell Biocatalysis in the Cyanobacterium Synechocystis

Photosynthetic organisms use sunlight to produce ATP and NADPH powering their metabolism. Harnessing these products for driving biocatalytic reactions would enable development of clean and sustainable alternatives for chemical reactions. In this study, we present the demonstration that ATP produced from the photosynthetic process can fuel a biocatalytic transformation in the whole-cell configuration. This result was achieved by expressing in the cyanobacterium Synechocystis sp. PCC 6803 an ATP-dependent enzyme, the gamma-glutamyl-methylamide synthetase from Methylovorus mays No. 9 (MmGMAS). The expressed enzyme was able to drive, in the transgenic strain, the light-driven biosynthesis of l-theanine. Consumption of ATP by the recombinant MmGMAS was even beneficial under strong illumination, protecting the photosynthetic electron transport from photodamage. These findings demonstrate the possibility of using photosynthetic microorganisms like Synechocystis as a potential platform for sunlight driven biotransformations with wide potential biocatalytic applications. In this perspective, we further present the tridimensional structure of MmGMAS, which explains its promiscuous in vivo activity and provides the basis for its rational evolution.