Group finds circadian clock common to almost all life forms
By BOB YIRKA - PHYSORG.COM
Added: Fri, 18 May 2012 12:38:36 UTC
The peroxiredoxin active site is highly conserved in all domains of life. Image: Nature (2012) doi:10.1038/nature11088
Phys.org) -- A group of biology researchers, led by Akhilesh Reddy from Cambridge University have found an enzyme that they believe serves as a circadian clock that operates in virtually all forms of life. In a paper published in the journal Nature, they describe a class of enzymes known as peroxiredoxins which are present in almost all plants and other organisms and which appear to serve as a basic ingredient in non-feedback loop biological clocks.
Up till now, researchers have not been able to find any kind of common biorhythmic clock among the Earth’s varied organisms, each class seemed to have its own. They did find though that one common feature of most was a feedback loop, which is where genes are transcribed before being translated into proteins which then build up until they reach a tipping point. Once that happens, transcription is turned off and the enzyme goes dormant. This cycle, for most organisms occurs on a twenty four hour basis, and is responsible for such things as the feelings of sleepiness or hunger in people that occur at roughly the same time each day.
But now, this new research suggests that the true clock controlling behavior in virtually every imaginable plant, animal, fungus, etc. has its roots in an enzyme whose purpose is to help clean up residue left over from the ravages of antioxidants.
Peroxiredoxins, which exist in virtually all life forms, are enzymes that cycle between two states depending on whether they have reacted recently with hydrogen peroxide, or not. The researchers found that this cycle occurs on a roughly twenty four hour cycle in all of the organisms they’ve tested to date. What’s more, the cycle continued even in the absence of light, proving that it’s not part of a feedback loop. Unfortunately, the team has not yet been able to show how or if the enzyme controls other clock mechanisms that are a part of feedback loops.
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