30–40%. In the case of 5′-AMP photophosphorylation, the yield of ATP was ten times lower (Kritsky, Kolesnikov and Telegina, 2007). In the other model, the photophosphorylation process was sensitized by abiogenic flavin pigment present in flavoproteinoid microspheres formed after a self-assembly in selleck inhibitor aqueous medium of the products of thermal condensation of a mixture of glycine, glutamic acid and lysine. The process was induced both by the UVA- and visible (blue) radiation. The yield of ATP after ADP phosphorylation was ca. 20–30% and the yield of ATP formed as a result of 5′-AMP photophosphorylation
was about 10% (Kritsky, Kolesnikov and Telegina, 2007; Kolesnikov, Telegina, Lyudnikova, and Kritsky, 2008). The photophosphorylation system was active under oxygenic conditions. In the deaerated medium it showed a full activity in case H2O2 or an alternative, non-oxygenic selleck chemical electron acceptor such as Fe3+-cytochrome c were present. The phosphorylation mechanism
has no analogs in organisms. It likely involves a direct interaction of semiquinone flavin molecule with ADP, the formation of ADP radical and its phosphorylation by orthophosphate. Supported by Presidium of Russian Academy of Sciences, Program of Basic Research No 18 and by grants from Russian Foundation for Basic Research No 07-04-00460-a and No 06-04-90599 BNTS_a. Kritsky, M.S., Kolesnikov, M.P., and Telegina, T.A., (2007) Modeling of abiogenic 5-Fluoracil chemical structure synthesis of ATP. Doklady Biochemistry and Biophysics, 417:313–315. Kolesnikov, M.P., Telegina, T.A., Lyudnikova, Smoothened inhibitor T.A., and Kritsky, M.S., (2008) Abiogenic photophosphorylation of ADP to ATP sensitized by flavoproteinoid microspheres. Origins of Life and Evolution of Biosphere,
38(3): 243–255. E-mail: [email protected]ras.ru Oxaloacetate-to-Malate Conversion by Mineral Photoelectrochemistry: Implications for the Viability of the Reductive Tricarboxylic Acid Cycle in Prebiotic Chemistry Marcelo I. Guzman, Scot T. Martin School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, U.S.A. 02138 There are five known mechanisms by which autotrophic organisms fix carbon (Thauer, 2007). Of these, however, a reductive tricarboxylic acid (rTCA) cycle, has been proposed as the most plausible metabolic pathway of CO2 fixation at the time life originated (Wachtershauser, 1990). Moreover, the carboxylic acids produced by the rTCA cycle are possibly a biosynthetic core of initial life (Smith and Morowitz, 2004). Recently, some of the endoergic reductive steps of the rTCA cycle were demonstrated as feasible through mineral photoelectrochemistry by the semiconductor mineral ZnS (Zhang and Martin, 2006). In this context, the reductive conversion kinetics of oxaloacetate (OAA) to malate (MA) by ZnS mineral photoelectrochemistry were studied from 5 to 50°C at pH = 7.