Two-pathway enzyme interpreted as result of evolution

This is an interesting bit of biological news:

Working with colleagues from FSU, Duke University and Brandeis University, …[Yang] recently produced remarkable computer models of an enzyme that carries the unwieldy name of inosine monophosphate dehrydrogenase, or IMPDH for short. IMPDH is responsible for initiating certain metabolic processes in DNA and RNA, enabling the biological system to reproduce quickly.

“In creating these simulations of IMPDH, we observed something that hadn’t been seen before,” Yang said. “Previously, enzymes were believed to have a single ‘pathway’ through which they deliver catalytic agents to biological cells in order to bring about metabolic changes. But with IMPDH, we determined that there was a second pathway that also was used to cause these chemical transformations. The second pathway didn’t operate as efficiently as the first one, but it was active nevertheless.”

Why would an enzyme have two pathways dedicated to the same task? Yang and his colleagues believe that the slower pathway is an evolutionary vestige left over from an ancient enzyme that evolved over eons into modern-day IMPDH.

The finding is significant for several reasons, Yang said.

“First of all, this offers a rare glimpse of evolutionary processes at work on the molecular level,” Yang said. “Typically when we talk about evolution, we’re referring to a process of adaptation that occurs in a population of organisms over an extended period of time. Our research examines such adaptations at the most basic level, which helps scientists to develop a fuller picture of how evolution actually occurs.

Science Daily article

The computational aspects of the discovery are significant as well, since the structure of the enzyme was predicted by computer modeling.

There is no certainty at present that the less efficient enzymatic pathway is the older one, of course.  Yet it may be a tantalizing glimpse into the evolutionary development of biochemical pathways.  Of course, the article available to us via the web gives us little detail, however this does seem to be a potentially significant development in our knowledge of evolution, thus worthy of present and future attention.

I should point out that there is nothing new about an enzyme catalyzing two different reactions.  What is new, as far as I know, is one enzyme utilizing two different pathways for the production of one product.

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