Glutamine: History and Discovery

Glutamine has an unusual place in the history of chemistry: it was given a name a full decade before anyone had actually held it in their hands. In 1873 two chemists predicted that such a substance ought to exist and christened it — and only in 1883 did the German chemist Ernst Schulze, working with E. Bosshard, finally isolate it, not from muscle or blood but from the juice of the humble sugar beet. This article traces what the historical record actually supports: the discovery of the parent acid that glutamine is named after, the bold naming of a molecule that had never been seen, its eventual isolation, the awkward chemistry that kept it hidden inside proteins for another half-century, and the twentieth-century work — above all by Hans Krebs — that turned a beet-juice curiosity into one of the most-studied amino acids in medicine. Where the record is firm we say so; where a detail is uncertain or disputed, we flag it.

Table of Contents

  1. What's in the Name: From Gluten to Glutamine
  2. A Molecule Named Before It Was Found (1873)
  3. Isolation from Beet Juice: Schulze and Bosshard, 1883
  4. Ernst Schulze and the Amino-Acid Harvest
  5. The Amino Acid That Hid Inside Proteins
  6. The Wider Story: Protein, Peptides, and the Amino-Acid Era
  7. Hans Krebs and the Birth of Glutamine Biochemistry
  8. From Beet Juice to the Clinic
  9. Research Papers and References
  10. Connections
  11. Featured Videos

What's in the Name: From Gluten to Glutamine

To understand where the word glutamine comes from, you have to start one molecule earlier, with glutamic acid (the substance the body knows as glutamate). Glutamic acid was discovered in 1866 by the German agricultural chemist Karl Heinrich Ritthausen, who broke down wheat gluten with acid and separated out a new compound. He called it Glutaminsäure in German — literally "gluten acid" — because it came from gluten (the word itself traces back to the Latin gluten, meaning "glue," a nod to the sticky, gluey character of wheat dough). That single naming decision set the pattern for a whole small family of related molecules.

Glutamine's name was then built directly on top of glutamic acid's. Chemically, glutamine is the amide of glutamic acid — the same carbon skeleton, but with one of its acid groups capped by an extra nitrogen-bearing "amide" unit. Chemists mark that amide relationship with the ending -ine (in German, -in), so Glutaminsäure (glutamic acid) gives Glutamin (glutamine). This is exactly the same naming logic that links asparagine to aspartic acid: in each pair, the "-ine" member is the amide of the corresponding acid. So the name glutamine carries two layers of history at once — the wheat gluten it ultimately descends from, and the chemical kinship to glutamic acid that the "-ine" ending announces.

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A Molecule Named Before It Was Found (1873)

One of the genuinely surprising facts about glutamine is that it was named before it was ever isolated — it is one of only a couple of amino acids with that distinction. The prediction came in 1873, in a study of how proteins break down, published by the chemists Heinrich Hlasiwetz and Josef Habermann. When they took the milk protein casein apart with acid, the products they could account for — glutamic acid, aspartic acid, leucine, tyrosine — came with a conspicuous amount of free ammonia that had to have come from somewhere.

Hlasiwetz and Habermann reasoned that this extra, loosely held nitrogen pointed to a hidden precursor: a nitrogen-richer relative of glutamic acid that the harsh acid had torn apart, liberating ammonia in the process. By straightforward analogy with glutamic acid, they proposed the name Glutamin for this still-hypothetical substance. In other words, glutamine began life as an inference — a name attached to a gap in the chemical bookkeeping — rather than as a bottle of crystals on a laboratory bench. That gap would not be filled for another ten years.

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Isolation from Beet Juice: Schulze and Bosshard, 1883

The predicted molecule finally became a real, isolated substance in 1883. The German chemist Ernst Schulze, working with his collaborator E. Bosshard, obtained glutamine in crystalline form — and the source was a memorable one. They did not extract it from meat, blood, or muscle, where glutamine is in fact most abundant in the living body, but from the juice of the sugar beet (Beta vulgaris). Their report — titled "Ueber das Glutamin" — appeared in the German chemistry journal Berichte der deutschen chemischen Gesellschaft (the "Reports of the German Chemical Society"). The American Chemical Society, in its reference profile of the molecule, dates the isolation to this 1883 work by "Ernst Schulze and E. Bosshard" from sugar-beet juice.

Why a beet, of all things? Plants build up free amino acids as a way of storing and moving nitrogen, and the sugar beet happens to accumulate generous amounts of free glutamine in its sap — far more, relative to everything else dissolved there, than is conveniently extractable from animal tissue. That made beet juice an ideal hunting ground for a chemist trying to fish out a single new compound. It is a small irony of glutamine's story that the amino acid now famous as the body's most abundant was first captured from a vegetable rather than from us. (Decades later, beet juice remained such a practical source that researchers were still publishing improved methods for "the preparation of glutamine from beet juice" well into the twentieth century.)

The 1883 isolation closed the loop opened in 1873: the substance Hlasiwetz and Habermann had only been able to predict from missing nitrogen now existed as something you could weigh, crystallize, and study. The hypothesis had become a chemical.

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Ernst Schulze and the Amino-Acid Harvest

Ernst Schulze (1840–1912) was a German chemist who spent four decades at the polytechnic in Zürich, where from 1872 he held the chair of agricultural chemistry. He belongs to the great nineteenth-century generation that, piece by piece, took proteins apart and worked out which amino acids they were made of. Plants — seedlings, sprouts, and storage organs rich in free amino acids — were his favourite raw material, which is why so many of his discoveries came from sources like beets and germinating seeds rather than from animal tissue.

Schulze and his students are credited with first isolating several amino acids now regarded as fundamental, glutamine among them. He is also credited with the discovery of arginine — which he obtained from lupin seedlings, reported in 1886 with his collaborator Ernst Steiger — and with the discovery of phenylalanine (isolated in 1879 with Giovanni Barbieri, also from lupin seedlings). Glutamine therefore sits within a remarkable run of results from a single laboratory: an agricultural-chemistry program that, almost as a by-product of studying how plants handle nitrogen, helped map out the building blocks of all protein.

One honest note about the record. Standard biographical accounts of Schulze list glutamine, arginine, and phenylalanine among his lab's discoveries but do not always name his individual co-workers for each compound; the specific attribution of the 1883 glutamine isolation to Schulze and Bosshard comes from the chemical and historical literature on the molecule itself. Both names are reported together for that work, and we present them that way.

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The Amino Acid That Hid Inside Proteins

Isolating glutamine from beet juice in 1883 was one thing; proving it was a genuine building block of proteins turned out to be much harder, and the reason is a quirk of chemistry worth understanding. For most of the nineteenth and early twentieth centuries, the standard way to find out what a protein was made of was to boil it in strong acid until it fell apart into its component amino acids, then identify the pieces. But that very method destroys glutamine: hot acid strips off glutamine's amide nitrogen and converts it straight into glutamic acid (releasing ammonia — exactly the ammonia Hlasiwetz and Habermann had noticed in 1873).

The consequence was that whenever chemists hydrolysed a protein, any glutamine it contained showed up in the analysis as glutamic acid plus a puff of ammonia. Glutamine was, in effect, invisible to the main analytical tool of the era — present in the protein, but erased at the moment of measurement. This is why its true status as a protein constituent stayed in doubt long after it had been isolated as a free compound.

The puzzle was resolved in 1932, when researchers at Imperial College in London used a gentler approach — breaking proteins down with enzymes rather than acid — and were thereby able to recover glutamine (and asparagine) intact, demonstrating that these amides really are present in proteins as themselves, not merely as artefacts of the acids they decompose into. That gentle-digestion proof finally settled glutamine's place in the protein alphabet, roughly half a century after Schulze and Bosshard first held the pure substance.

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The Wider Story: Protein, Peptides, and the Amino-Acid Era

Glutamine's discovery makes more sense set against the broader nineteenth-century effort to understand what living matter is built from. The very word protein dates to 1838: the Dutch chemist Gerardus Johannes Mulder described the substances, and the Swedish chemist Jöns Jacob Berzelius suggested the name, drawing on the Greek proteios ("primary," "of first rank") to capture how fundamental these materials seemed to life. Across the following decades chemists set about isolating, one at a time, the amino acids that proteins are composed of.

That hunt had begun even earlier. The first amino acid ever isolated was asparagine, obtained from asparagus juice in 1806 by the French chemists Louis Nicolas Vauquelin and Pierre Jean Robiquet — and, like glutamine, it was named after the plant it came from. Through the 1800s the list grew: glycine from gelatin (Henri Braconnot, 1820), glutamic acid from gluten (Ritthausen, 1866), glutamine from beet juice (Schulze and Bosshard, 1883), and many more, until the full roster of about twenty protein amino acids was complete by the 1930s.

The other half of the picture was working out how amino acids join together to form a protein. That achievement is associated above all with the German chemist Emil Fischer, who around the turn of the century established that amino acids are linked by what he named the peptide bond, and who synthesized the first simple peptides (beginning with glycyl-glycine in 1901). Fischer received the 1902 Nobel Prize in Chemistry — awarded specifically for his earlier work on sugars and purines — and his peptide research, carried out in the same era, supplied the structural grammar that explains how a building block such as glutamine takes its place in a protein chain. Glutamine, in short, was discovered right in the middle of the period when science was learning both the parts of proteins and the rules for assembling them.

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Hans Krebs and the Birth of Glutamine Biochemistry

If the nineteenth century discovered glutamine, the twentieth century discovered what it does. The pivotal early figure here is Hans Krebs — the same Krebs later celebrated for the citric-acid (Krebs) cycle and a 1953 Nobel Prize. In 1935, shortly after moving to England, Krebs published foundational work on how animal tissues handle glutamine. He described the enzyme glutaminase, which splits glutamine to release glutamic acid and ammonia, and he studied the reverse process by which tissues build glutamine from glutamic acid and ammonia — the basic chemistry by which the body packages and transports nitrogen.

Krebs also noticed something subtle that still matters today: the glutamine-splitting activity behaved differently in different organs — the "brain-type" enzyme being held in check by its own product (glutamate) in a way the "liver-type" was not. These 1935 observations were the first real molecular insights into glutamine metabolism, and historians of the field trace the modern medical and nutritional interest in glutamine directly back to them. Krebs himself kept returning to the molecule over the following decades, helping show that glutamine is a major fuel and nitrogen source for the gut, the kidneys, and the immune system.

It is worth marking the difference between the two kinds of discovery in this article. Schulze and Bosshard discovered the substance; Krebs and his successors discovered its biology. The beet-juice crystals of 1883 told the world that glutamine existed; the enzyme studies of 1935 onward began to explain why a body would bother making so much of it.

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From Beet Juice to the Clinic

The line that runs from a nineteenth-century curiosity to a modern clinical tool is unusually direct for glutamine. Once Krebs and others had established that glutamine fuels rapidly dividing cells — the cells lining the intestine, the cells of the immune system — researchers began asking whether supplying extra glutamine could help patients whose own reserves were being drained by serious illness, surgery, or burns. By the late twentieth century this had grown into a large body of clinical research, and glutamine had earned its now-standard description as a "conditionally essential" amino acid: one the body usually makes for itself, but cannot always make fast enough under heavy stress.

Glutamine's metabolism later took on yet another life in cancer research, where the appetite of fast-growing tumour cells for glutamine — a phenomenon whose roots, again, trace back to Krebs's 1935 work — became a target of study in its own right. The arc is striking: a molecule first predicted from missing ammonia in 1873, captured from beet sap in 1883, vindicated as a true protein constituent in 1932, and given its biochemical meaning from 1935 onward, is today investigated in gut health, critical care, sports nutrition, and oncology alike.

Two honest cautions belong at the close of any history like this. First, the fact that glutamine has a long and well-documented scientific pedigree says nothing, by itself, about whether any particular supplement use is effective or safe — that is a separate question, tested by clinical trials, and the evidence is genuinely mixed across different uses. Second, the modern story includes findings that temper early enthusiasm, including large critical-care trials that did not show the benefit researchers had hoped for. The detailed evidence, mechanisms, dosing, and cautions are covered on the main Glutamine page and in the companion Glutamine Benefits articles; this history is concerned only with how the molecule came to be known in the first place.

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Research Papers and References

The list below combines peer-reviewed sources on glutamine's chemistry and metabolic history with curated PubMed topic-search links into the historical and biochemical literature. The earliest primary sources — the 1873 prediction by Hlasiwetz and Habermann, the 1883 isolation by Schulze and Bosshard ("Ueber das Glutamin," Berichte der deutschen chemischen Gesellschaft, vol. 16, pp. 312–315), and Ritthausen's 1866 discovery of glutamic acid — are named in the article as historical sources; the original nineteenth-century papers predate online indexing and are not directly linkable. Author names, titles, and journals are given as plain text; only the stable DOI, PMID, or archive link is hyperlinked, and each opens in a new tab.

  1. Rider AA, McCollum EV. The preparation of glutamine from beet juice. Archives of Biochemistry and Biophysics. 1957;68(1):39-41. — doi:10.1016/0003-9861(57)90324-7 (PMID: 13435892)
  2. Altman BJ, Stine ZE, Dang CV. From Krebs to clinic: glutamine metabolism to cancer therapy. Nature Reviews Cancer. 2016;16(10):619-634. — doi:10.1038/nrc.2016.71 (PMID: 27492215)
  3. Cruzat V, Macedo Rogero M, Noel Keane K, Curi R, Newsholme P. Glutamine: metabolism and immune function, supplementation and clinical translation. Nutrients. 2018;10(11):1564. — doi:10.3390/nu10111564 (PMID: 30360490)
  4. Newsholme P. Why is L-glutamine metabolism important to cells of the immune system in health, postinjury, surgery or infection? Journal of Nutrition. 2001;131(9 Suppl):2515S-2522S. — PMID: 11533304
  5. L-Glutamine — Molecule of the Week. American Chemical Society. — acs.org: L-Glutamine (isolation by Schulze & Bosshard, 1883)
  6. Glutamine — history and discovery of the amino acid — PubMed: glutamine history and discovery
  7. Glutamine metabolism — history and biochemistry — PubMed: glutamine metabolism, Krebs, and glutaminase

External Authoritative Resources

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Connections

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