Tracing Life’s Sweet Beginnings: A Closer Look at the Birth of Earth’s Primitive Sugars

In an innovative proposition, the earliest sugars are believed to have stemmed from glyoxylate, illustrated as the central molecule. The proposed theory suggests that glyoxylate initially interacts with itself, subsequently leading to byproducts that ultimately form uncomplicated sugars and other compounds, shown as surrounding molecules. This research was undertaken by Scripps Research and Unsplash.

Scientists from Scripps Research and the Georgia Institute of Technology, specialized in investigating life’s origins, propose that glyoxylate might have been the primary sugar provider on the prebiotic, or early life, Earth.

The chemists recently published a novel theory concerning the emergence of the initial sugars, a critical factor in life’s evolution, on the ancient Earth in the esteemed Chem journal.

Their theory posits that fundamental sugars essential for forming the earliest life forms could have originated from reactions involving glyoxylate (C2HO3–), a relatively simple chemical likely present on Earth before life’s evolution.

“Our new theory presents significant advantages over the more conventional idea that primitive sugars sprang from the chemical formaldehyde,” declares Ramanarayanan Krishnamurthy, Ph.D., a chemistry professor at Scripps Research.

Charles Liotta, Ph.D., Regents’ Professor Emeritus at the School of Chemistry and Biochemistry at the Georgia Institute of Technology, co-authored the study with Krishnamurthy.

Chemists focused on life’s origins strive to elucidate how the necessary molecular building blocks and reactions for life could have sprung from simple chemicals likely existing on the prebiotic Earth. Their ultimate goal is to comprehend how our vibrant planet came into existence. Their findings also contribute to numerous other scientific disciplines, ranging from atmospheric science and geology to synthetic biology and the quest for extraterrestrial life.

Origin-of-life chemistry has to explain the existence of three significant classes of biological molecules: the amino acids constituting proteins, the nucleobases that form the “alphabet” of DNA and RNA, and the sugars or carbohydrates present throughout biology, including within DNA and RNA’s helical backbone. Prevailing theories suggest amino acids likely derived from ammonia (NH3), while nucleobases emerged from hydrogen cyanide (HCN).

However, the genesis of sugars remains somewhat ambiguous. Many researchers argue that the first sugars resulted from reactions involving formaldehyde (CH2O), but this concept has certain limitations.

Liotta comments, “The reactions involving formaldehyde proposed by this theory are quite chaotic—they entail uncontrolled side reactions and other issues due to formaldehyde’s high reactivity under presumed early-Earth conditions.”

The chemists suggest an alternative “glyoxylose reaction” scenario where glyoxylate reacts with itself initially, producing a molecule related to formaldehyde known as glycolaldehyde. They propose that glyoxylate, glycolaldehyde, their byproducts, and other simple compounds could have continued interacting, ultimately producing simple sugars and other products—without the complications associated with formaldehyde-based reactions.

Glyoxylate already holds a significant place in theories of life’s origin. In 2007, Swiss chemist Albert Eschenmoser suggested a variant of it might have been the source for several primitive biomolecules. In a 2020 article in Nature Chemistry, Krishnamurthy and Greg Springsteen, Ph.D., a chemist from Furman University, also proposed that glyoxylate might have facilitated the onset of a primordial version of the contemporary TCA (tricarboxylic acid) cycle, a fundamental metabolic process found in most life forms on Earth.

Krishnamurthy and his team are presently laboring to verify in a laboratory setting that the glyoxylose reaction scenario could have indeed given rise to the first sugars.

“Providing such proof would underscore the versatility of glyoxylate in prebiotic chemistry and further stimulate the quest for its own origin on the prebiotic Earth,” says Krishnamurthy.

The researchers are also exploring potential commercial applications of reactions that produce glyoxylate, since these effectively utilize CO2 and can be employed to reduce CO2 levels, either locally in industrial environments or globally to combat climate change.

Reference: “The potential of glyoxylate as a prebiotic source molecule and a reactant in protometabolic pathways—The glyoxylose reaction” by Ramanarayanan Krishnamurthy and Charles L. Liotta, 13 April 2023, Chem. DOI: 10.1016/j.chempr.2023.03.007

The NASA Exobiology Program NNH20ZA001N-EXO, the National Science Foundation, and the NASA Astrobiology Program under the Center for Chemical Evolution supported this study.

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More about Origins of Earth’s First Sugars

• Scripps Research
• Georgia Institute of Technology
• Chem
• Nature Chemistry
• NASA Exobiology Program
• National Science Foundation
• NASA Astrobiology Program
• Center for Chemical Evolution
• Albert Eschenmoser
• Formaldehyde
• Glyoxylate