Energy for the Origin of Life

Abstract

In our universe, life may exist on many planets, more or less similar to Tellus, the Earth. As the only life we know is life on Earth, our ideas about life in the universe are naturally based on what we know about this life and its various aspects, such as its origin from an energetic point of view. Life has been characterized in terms of a specific flow of energy, matter and information. The transition from general molecular information to specific genetic information, resulting in an energy requiring process of replication of a kind allowing for mutations and natural selection, may be considered as a most essential anastrophe (H. Baltscheffsky, 1997) in the chains of events resulting in the origin and subsequent evolution of life. Before, during and after its origin, particularly significant energy sources may have been light energy and chemical energy. The metabolism of living cells is known to be based on their capacity for capture and conversion of energy, with energy coupling allowing the energy requiring reactions to be driven by those reactions, which under prevailing conditions can supply the necessary energy. Among the many still open questions about the energetics of the origin of life are: 1) was the source of energy for the origin of life photic or chemical or both, and were there other significant energy sources, such as electrical discharges etc.?; 2) were the first energy-rich chemical compounds of late chemical or early biological evolution inorganic or organic or of both kinds?; and 3) were there several systems for energy conversion at the prenucleotide level, such as, for example, those which have been suggested to be based on inorganic pyrophosphate ("PPi world"), organic thioesters ("thioester world") and iron-sulphur compounds ("iron-sulphur world"), and were there close chemical links between such "worlds"? Some major anastrophic transitions in the energetics of the origin and early evolution of life will be presented. Our search for very early or "primitive" enzymes will be discussed, with examples taken from recent results with both soluble and membrane-bound inorganic pyrophosphatases (PPases).