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Metabolic inheritance Eörs Szathmáry Collegium Budapest AND Eötvös University The formose ‘reaction’ formaldehyd e autocatalysi s glycolaldehyde Butlerow, 1861 Von Kiedrowski’s replicator Replication in the formose reaction • • • • • Replication is non-informational Autocatalysis – YES Heredity – NO Good for metabolism Not good for genetics Gánti’s chemoton model (1974) metabolism template copying membrane growth ALL THREE SUBSYSTEMS ARE AUTOCATALYTIC Is this just logical or also historical order? • How much evolution did take place (presumably on surfaces) before protocells appeared? The latest edition: OUP 2003 • After several editions in Hungarian • Two previous books (the Principles and Contra Crick) plus one essay • Essays appreciating the biological and philosophical importance Pathways of supersystem evolution metabolism MB boundary MT template BT MBT INFRABIOLOGICAL SYSTEMS Contemporary autocatalytic biochemical cycles • The Calvin cycle (sugar-phosphate making more sugar-phosphate) • Reverse citric acid cycle Primitive ancestry of the reverse citric acid cycle • Was proposed by Günter Wächtershäuser (1990) • Coupled to CO2 fixation and pyrite formation around deep-sea hydrothermal vents The archaic version • He even imagined alternative („mutant”) cycles • No experimental evidence so far Units of evolution (JMS) 1. multiplication 2. heredity 3. variation hereditary traits affecting survival and/or reproduction Classification of replicators Limited heredity Holistic formose Modular Von Kiedrowski Unlimited heredity genes Limited (# of individuals) (# of types) Unlimited (# of individuals) << (# of types) King (1980): evolution of the coenzymes • He looked at the metabolic maps then • Coenzymes looked auto- and cross-catalytic • BUT the situation is slightly more complicated • The idea nicely links to the assumed primitive ancestry of coenzymes (related to the idea of the RNA world) An autocatalytic cycle in the given environment Although A is autocatalytic, it is not strictly needed Dependent on the environment! Autocatalysis of the pair (A, B) is more complicated, but easy to see If this is big, you may not realize the autocatalysts The basic question • Could one kick-start metabolism just with external molecules and macromolecules (genes an enzymes)? • Influx buildup of metabolism? What to do? Work with B. Papp and Á. Kun • Use Heinrich’s scope analyis to identify absolutely essential INTERNAL molecules • Look for those molecules that yield the largest increase in metabolic scope • Stop when there is a functional metabolism • Check the results with flux balance analysis (FBA) for the producible compounds in steady state Autocatalytic synthesis of CoA in Synechocysts sp. • Note: the same cofactor can be autocatalytic in different ways in different organisms Metabolic networks Environmental dependence • E. coli network under a condition where only glucose and inorganic compounds were included in the food set. • In addition to ATP, NAD, CoA and quinones were also identified as autocatalytic seeds under this condition Conlusions • • • • • Essentially, Gánti and King were right There IS an autocatalytic seed At least one coenzyme is always in the seed BUT the set is environment-dependent Puts constraints on artifical (re)construction of (proto)cells • BIOINFORMATICS HELPS ANSWER OLD, FUNDAMENTAL QUESTIONS