Water is considered the key ingredient for the existence of life forms. Astronomers looking for life on the other planets in the solar system and elsewhere in the universe always begin by checking for the availability of water. The presence of water molecules on a terrestrial body is thought to be the fundamental requirement for the evolution and existence of life on it. It is also the green signal to continue the search for life on a planet or planetoid.
But now biochemists have begun seriously inquiring into the chemical constituents of life and their role in the existence of life elsewhere. They point out, in a commentary in the current issue of Science on two recent studies looking at iron enzymes, the possible role of other elements, such as iron which adds hemoglobin to the red blood cells that carry oxygen. They think that the chemistry of such elements might explain the existence of life here on earth.
Carrie Wilmot, a biochemist in the University of Minnesota, comments ‘It is interesting to wonder what life would be like at this point if iron were less abundant‘.
A recent study by Gergely Katona of Universite J. Fourier in France and her team, answers the question how some simple life forms like the bacteria and the microbes called archaea, methane-releasing bugs found in extreme environments, use an iron-based enzyme called ‘superoxide reductase‘ to take oxygen and turn it into a more manageable hydrogen peroxide. The enzyme works as an antioxidant and helps the microbes avoid the damage reactive oxygen would do to single-celled creatures.
An iron-centered enzyme called ‘ring-cleaving dioxygenase’, which is widely used in environmental clean-ups, is studied by Elena Kovaleva and John Lipscomb, also of the University of Minnesota.
A new technique, partly pioneered by Wilmot, is used in both the studies - researchers quick-freeze enzymes in action as they trigger rapid chemical reactions. These studies have found an intricate rearrangement of molecules in the iron-based enzymes as they induce reactions.
Wilmot says ‘the study of microbial enzymes raises big questions about life‘. ‘Iron enzymes like the ones in the study helped simple life forms breathe and burn the oxygen in the atmosphere for energy’ she adds. Enzymes speed up chemical reactions and cause release of energy that makes complex life possible.
Astronomers, on the other hand, continue their search for life elsewhere in the universe by first looking for traces of water. Astronomers in the Lowell Observatory revealed this month the first detection of water molecules in the atmosphere of a nearby star’s planet.
The new proposition from the biochemists may fundamentally transform the way scientists view the circumstances that favoured the evolution of life on earth. Further, this may very well guide the search for extra-terrestrial life in a new direction.
