Essentiality is an emergent property of metabolic network wiring

The topological bases of essentiality in the yeast metabolic network from the perspective of double mutations are the subject of this study. A strong relationship between essentiality and the 'missing alternative' topological property is shown in terms of the presence of multiple genes synthesizing the same enzyme, supplementary enzymes participating in the same metabolic reaction, and availability of other pathways in the graph connecting the separated nodes after the knockouts. We demonstrate that the 'missing alternative' paradigm is sufficient to explain the generation of essentiality for double mutations in which each single deleted element is non-essential. (c) 2007 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.