Gil Benko, Chad Knutson, Jerzy Maselko, Fouzi Mouffouk, Tristan Rocheleau
Paper #: 06-12-047
A key requirement of an autonomous self-replicating molecular machine, a protocell, is its ability to digest resources and turn them into building blocks. Thus a protocell needs a set of metabolic processes fueled by external free energy e.g. in the form of available chemical redox potential or light. We introduce and investigate a minimal photo-driven metabolic system, which is based on photofragmentation of resource molecules catalyzed by genetic molecules. We represent and analyze the full metabolic set of reaction kinetic equations and through a set of approximations simplify the reaction kinetics such that analytical expressions can be obtained for the building block production. The analytical approximations are compared to the full equation set and with corresponding experimental results to the extent they are available. It should be noted, however, that the proposed metabolic systems is not yet fully experimentally implemented and tested so this investigation is conducted to obtain a deeper understanding of its dynamics and to map out its limitations. We demonstrate that this type of minimal photo-driven metabolic scheme is typically rate limited by the front-end photoexcitation process while its yield is determined by the genetic catalysis. We further predict how gene catalyzed metabolic reactions only can undergo evolutionary selection for certain combinations of the involved reaction rates due to their intricate interactions. We finally discuss how the expected range of metabolic rates likely impact the other key protocellular processes such as container growth and division as well as gene replication.