New primordial pathway to life's chemical building blocks discovered

Washington, Feb 1 (ANI): A new study led by Indian origin scientists has proven a new pathway to produce sugars indispensable for life to begin.

For decades, chemists considered a chemical pathway known as the formose reaction the only route life's chemical building blocks, but more recent research has called into question the plausibility of such thinking.

Now a group from The Scripps Research Institute has shown the plausibility of an alternative pathway to those sugars called the glyoxylate scenario, which may push the field of pre-life chemistry past the formose reaction hurdle.

"We were working in uncharted territory," says Ramanarayanan ("Ram") Krishnamurthy, a Scripps Research chemist who led the research.

"We didn't know what to expect but the glyoxylate scenario with respect to formation of carbohydrates is not a hypothesis anymore, it's an experimental fact."

In 2007, Albert Eschenmoser, an organic chemist who recently retired from Scripps Research, proposed a new pathway he dubbed the glyoxylate scenario.

This involved glyoxylate as an alternative starting point to formaldehyde, and reactions with dihydroxyfumarate (DHF) that Eschenmoser hypothesized could launch a cascade of reactions that would lead to sugars.

Glyoxylate was a good starting point because of the possibility that it could be produced by oligomerization of carbon monoxide under potentially prebiotic conditions.

Eschenmoser and Krishnamurthy began developing the experiments to test the hypothesis. At the time, very little was known about relevant reactions involving DHF, and nothing beyond theory about how it reacted with glyoxylate.

The idea that DHF might be involved in a plausible biosynthetic pathway to sugars (via a decarboxylative conversion to glycolaldehyde which aldolizes to sugars) dates back about as far as work on the formose reaction, but the experiments proved otherwise, causing DHF to fall from focus.

"We were thrown a lot of curve balls we had to really think through," said Krisnamurthy of the years he spent working with postdoctoral fellow Vasu Sagi, who is lead author of the new paper.

The team's experiments revealed that under the right conditions, DHF and glyoxylate, when in the presence of a few other plausible prebiotic chemicals including formaldehyde, would produce sugars known as ketoses.

Ketoses in turn can be converted to critical sugars, including some essential to forming certain amino acids, the DNA and RNA building blocks such as ribose.

Such efficiency is so rare in prebiotic chemistry and was so unexpected in the glyoxylate dihydroxyfumarate experiments, that the scientists were leery at first of their results.

"We had to prove it by repeating the experiments many times," Sagi added.

The study has been published in the Journal of the American Chemical Society. (ANI)