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.
Frequently Asked Questions (FAQs) about Origins of Earth’s First Sugars
What is the new hypothesis about the origin of Earth’s first sugars?
The new hypothesis suggests that the first sugars on Earth originated from glyoxylate, a simple chemical believed to have existed on Earth before life evolved. According to the hypothesis, glyoxylate reacted with itself and other simple compounds to form simple sugars and other products.
Who conducted the research on the origins of Earth’s first sugars?
The research was conducted by chemists from Scripps Research and the Georgia Institute of Technology.
What are the potential drawbacks of the theory that the first sugars came from formaldehyde?
The theory that the first sugars came from reactions involving formaldehyde has been criticized for the uncontrolled side reactions and high reactivity of formaldehyde under conditions believed to have existed on the early Earth. These factors could lead to messy and undesirable outcomes.
What role does glyoxylate already have in origin-of-life theories?
Glyoxylate has already been proposed as a source for multiple original biomolecules in origin-of-life theories. It’s also suggested that glyoxylate could have initiated a primordial version of the modern (tricarboxylic acid) TCA cycle, a fundamental metabolic process found in most life forms on Earth.
Are there any potential commercial applications for reactions that produce glyoxylate?
Yes, reactions that produce glyoxylate effectively consume CO2. Therefore, they can be used to reduce CO2 levels, either locally in industrial settings or globally to combat climate change.
More about Origins of Earth’s First Sugars
- Scripps Research
- Georgia Institute of Technology
- Nature Chemistry
- NASA Exobiology Program
- National Science Foundation
- NASA Astrobiology Program
- Center for Chemical Evolution
- Albert Eschenmoser