Glycine: History and Discovery

In 1820 a French chemist boiled a pot of gelatin with acid and crystallised out something unexpected: a sweet-tasting solid he was sure was a kind of sugar. He called it "sugar of gelatin." He was wrong about the sugar — but he had, without knowing it, taken an animal protein apart into one of its individual building blocks, among the very first times anyone had ever done so. That sweet crystal was glycine, and the story of how it was found, mis-named, re-named, and finally understood runs straight through the birth of biochemistry. This article traces what the historical record actually supports: who isolated glycine and from what, how its taste gave it the wrong name and then the right one, how it helped chemists work out what proteins are made of, and how the modern era revealed that the simplest amino acid of all is also one of the most quietly indispensable. Where the record is firm we say so; where a detail is uncertain or still discussed, we name it as such.

Table of Contents

  1. The 1820 Isolation: Sugar of Gelatin
  2. From Glycocoll to Glycine: The Naming Story
  3. Working Out the Structure
  4. Glycine and the Birth of Protein Chemistry
  5. Essential or Not? Rose and the Dietary Map
  6. The Glycine in Collagen
  7. The Modern Picture: Neurotransmitter and More
  8. What the History Tells Us
  9. Research Papers and References
  10. Connections
  11. Featured Videos

The 1820 Isolation: Sugar of Gelatin

Glycine was first isolated in 1820 by the French chemist and pharmacist Henri Braconnot (1780–1855), working in Nancy, France. Braconnot was a pioneer of a technique that would prove foundational to biochemistry: acid hydrolysis, the breaking down of a complex biological substance by boiling it with a strong acid. When he treated gelatin — the protein product obtained from boiling animal skin, bone, and connective tissue — with sulfuric acid, the large protein molecule was cleaved into smaller pieces, and from the resulting mixture he was able to crystallise a distinct new compound.

The crystals had a clearly sweet taste, and on that evidence Braconnot concluded he had obtained a sugar. He named it sucre de gélatine — literally "sugar of gelatin." This turned out to be a mistake, but an understandable and historically important one. Braconnot did not have the tools to know that his sweet crystal contained nitrogen, the element that distinguishes amino acids and proteins from true sugars. What he had actually done was far more significant than isolating a sweet compound: he had separated one of the individual building blocks out of which an animal protein is constructed — one of the earliest times anyone had achieved that. Glycine is therefore among the earliest amino acids ever isolated, and its discovery sits at the very beginning of the long effort to take proteins apart and find out what they are made of.

It is worth being precise about the priority here. Braconnot is consistently credited as the discoverer of glycine in 1820, and gelatin is consistently named as the source. The asparagine of Vauquelin and Robiquet (1806, from asparagus) is generally regarded as the first amino acid ever isolated, and several others — including leucine, which Braconnot himself also obtained from animal protein (muscle fibre) by the same acid process around 1820, and which Joseph Louis Proust had drawn from cheese a year earlier in 1819 — belong to the same remarkable early decades. Glycine is often described as among the first amino acids isolated from a protein by acid hydrolysis — the method that would eventually be used to take apart every protein and read off its amino-acid composition. Whether it was strictly the first, or stands beside Braconnot's own leucine from muscle, is reported differently in different sources, so we credit it as one of the earliest rather than claiming an outright first.

Back to Table of Contents

From Glycocoll to Glycine: The Naming Story

The name we use today was not the first, second, or even third attempt. Glycine's naming history is a small case study in how nineteenth-century chemistry corrected itself.

The first correction came in 1838, when the French chemist Jean-Baptiste Boussingault demonstrated that Braconnot's "sugar of gelatin" contained nitrogen. A true sugar contains only carbon, hydrogen, and oxygen; the presence of nitrogen proved that this sweet crystal was something else entirely. The "sugar" label could no longer stand.

A new name followed in 1847, proposed by the American chemist Eben Norton Horsford, then studying in Germany under the great chemist Justus von Liebig. Horsford suggested "glycocoll" (also spelled glycocoll or glycocolle), built from Greek roots meaning roughly sweet (glykys) and glue (kolla) — a fitting name for a sweet substance obtained from gelatin, which is essentially animal glue. The name captured both the taste and the source.

The final step came the very next year. In 1848 the eminent Swedish chemist Jöns Jacob Berzelius — one of the most authoritative voices in chemistry at the time — judged that "glycocoll" did not sit well alongside the names of the other known organic bases. Since sweetness was the compound's most distinctive feature, he proposed shortening the name to "glycine," directly from the Greek glykys (γλυκύς), meaning "sweet." That name stuck, and glycine has carried it ever since. Its sweet taste — the very property that fooled Braconnot into calling it a sugar — is preserved permanently in the name. (The older term "glycocoll" lingered in chemical and medical writing for many decades, which is why it still turns up in historical sources.)

Back to Table of Contents

Working Out the Structure

Knowing a compound's name and that it contains nitrogen is not the same as knowing what it actually is. Through the middle of the nineteenth century, chemists gradually pinned down glycine's molecular identity. A notable step is generally credited to the French chemist Auguste Cahours, who around 1858 showed that glycine could be understood as an amine of acetic acid — in modern terms, aminoacetic acid: an acetic-acid molecule carrying an amino (nitrogen-bearing) group. This places glycine's formula at C₂H₅NO₂, the simplest possible structure for an amino acid.

That simplicity is glycine's defining structural feature. Every other standard amino acid has a distinctive side chain hanging off its central carbon; glycine's "side chain" is merely a single hydrogen atom. It is the smallest of the twenty amino acids that build proteins, and the only one that is not chiral — it has no left-handed and right-handed mirror-image forms, because its central carbon carries two identical hydrogens. This is why, unlike most amino acids, glycine is never written with an "L-" or "D-" prefix: there is only one glycine. As later chemistry would reveal, that minimal size is not a curiosity but the key to several of glycine's most important biological jobs, where only the smallest possible building block will fit.

Back to Table of Contents

Glycine and the Birth of Protein Chemistry

Glycine's discovery did not happen in isolation; it was an early move in a much larger nineteenth- and early-twentieth-century project: figuring out what proteins are. Two milestones from that broader story are worth placing alongside glycine's own.

The first is the word "protein" itself. In 1838 — the same year Boussingault found nitrogen in glycine — the Dutch chemist Gerardus Johannes Mulder published work on the composition of animal substances, and the term protein (from the Greek proteios, meaning "primary" or "of first importance") was coined in connection with it, a coinage usually attributed to Berzelius — the same chemist who would name glycine ten years later. The idea was that these nitrogen-rich substances were the primary, fundamental stuff of living tissue.

The second milestone is how the building blocks are joined together. Around 1902, the German chemist Hermann Emil Fischer — and, independently and famously on the same day at the same meeting, Franz Hofmeister — advanced the understanding that proteins are chains of amino acids linked by what Fischer named the peptide bond. Fischer went on to synthesise such chains in the laboratory, demonstrating directly that amino acids could be strung together into protein-like molecules. Fischer received the Nobel Prize in Chemistry in 1902, though it is worth being accurate about the citation: the prize honoured his work "on sugar and purine syntheses," with his landmark protein and peptide work coming to fruition in the same period. Glycine, as the simplest amino acid, was a natural test subject in this era of taking proteins apart and putting them back together — it is the smallest, simplest link in the chains Fischer was learning to build.

Seen in this light, glycine is not just one compound among many. Isolated at the dawn of the field, named by the chemist who also helped name "protein," and the simplest unit in the peptide chains Fischer described, it is woven into the founding story of how we came to understand proteins at all.

Back to Table of Contents

Essential or Not? Rose and the Dietary Map

Isolating the amino acids was one project; working out which of them the human body can make for itself and which must come from food was another, and it took until the 1930s to finish. The central figure in that effort was the American biochemist William Cumming Rose (1887–1985). In 1935, Rose's laboratory isolated threonine — the last of the twenty standard amino acids to be discovered — after finding that a diet of the nineteen then-known amino acids could not support the growth of his laboratory rats. The missing factor turned out to be threonine, and its discovery completed the roster.

With all the amino acids in hand, Rose went on to perform the painstaking nitrogen-balance studies — first in rats, and later in human volunteers — that sorted the amino acids into two groups: those that are dietarily essential (the body cannot make them in adequate amounts, so they must be eaten) and those that are dietarily non-essential (the body can synthesise them itself). Glycine fell on the non-essential side of Rose's map: the human body can build it, principally from the amino acid serine, so a healthy adult does not strictly require glycine in the diet to avoid deficiency.

This is the proper historical context for a label glycine still carries — and for an important modern caveat. "Non-essential" meant only that the body can manufacture the amino acid; it never meant the amino acid is unimportant, and it did not measure whether the body can make enough for every demand. Much later work raised exactly that question for glycine, leading to the modern idea that it may be "conditionally essential" — made by the body, but possibly in amounts that fall short of full metabolic need during growth, stress, illness, or aging. That debate belongs to the modern era and is taken up on the companion Glycine Benefits pages; what matters for the history is that Rose's 1930s framework is where glycine was first formally classified, and where the language of "essential" and "non-essential" amino acids comes from.

Back to Table of Contents

The Glycine in Collagen

There is a fitting symmetry in glycine's history. Braconnot first isolated it from gelatin — and gelatin is nothing other than denatured collagen, the most abundant protein in the animal body. It would take more than a century to understand why gelatin was such a rich source of this particular amino acid, and the answer turned on glycine's tiny size.

Collagen has an unusual, highly repetitive structure: a long sequence in which every third position is glycine, giving the repeating pattern often written as Gly–X–Y. Glycine makes up roughly a third of all the amino acids in collagen. The reason was clarified once the protein's three-dimensional shape was worked out in the mid-1950s: collagen is a tight triple helix, three strands wound closely around one another, and the interior of that helix is so cramped that only the smallest possible amino acid will fit there. Glycine, with its single-hydrogen side chain, is the only residue small enough — so it must appear at every third position, on the inside of the coil, for the helix to form at all. The molecular model of the collagen triple helix is associated above all with the Indian biophysicist G. N. Ramachandran and his colleague Gopinath Kartha, whose work in the mid-1950s proposed the triple-helical structure.

This closes a loop that opened in 1820. The reason Braconnot pulled so much glycine out of boiled gelatin is the same reason collagen can hold its shape: collagen is built around glycine, the one amino acid small enough to occupy the heart of its triple helix. The earliest source of glycine and one of glycine's most important biological roles turn out to be the very same molecule. (Collagen is itself a protein rather than a single amino acid, and its fuller story is told on the dedicated Collagen page.)

Back to Table of Contents

The Modern Picture: Neurotransmitter and More

For its first century glycine was understood chiefly as a chemical curiosity and a building block of proteins. The twentieth century revealed that it is also an active signalling molecule in the nervous system — a discovery that reframed the "simplest" amino acid as one of the more versatile.

Glycine was shown to be a major inhibitory neurotransmitter, especially in the spinal cord and brainstem, where it acts on glycine receptors that quiet nerve signalling and help regulate movement and pain. At the same time, and seemingly in contradiction, glycine was found to be a required co-agonist at the NMDA receptor — an excitatory receptor central to learning and memory that cannot be activated by glutamate alone unless glycine is also bound to it. The same small molecule thus both calms and, in a different setting, helps switch on neural activity. This dual neurological role, layered on top of glycine's structural job in proteins and its many metabolic duties (in the synthesis of glutathione, creatine, heme, and bile acids), is why a compound once dismissed as a sweet contaminant of gelatin is now studied across sleep, metabolism, neurology, and healthy aging.

A final note from molecular biology rounds out the picture. When the genetic code was deciphered in the 1960s, glycine was found to be specified by an entire block of related codons — every three-letter code beginning GG (GGU, GGC, GGA, and GGG) — a tidy assignment for the smallest amino acid. The detailed evidence for glycine's modern clinical uses, mechanisms, dosing, and cautions is covered on the main Glycine page and the Glycine Benefits articles; this history is concerned only with how glycine came to be known.

Back to Table of Contents

What the History Tells Us

Glycine's history is, in miniature, the history of how we learned to read proteins. It begins with a careful experiment and an honest mistake — a sweet crystal that looked like sugar but was not. It moves through a chain of corrections by named scientists in named years: Boussingault finding the nitrogen in 1838, Horsford and Berzelius settling the name in 1847 and 1848, Cahours fixing the structure around 1858, Rose mapping its place in human nutrition in the 1930s, and the structural biologists of the 1950s explaining why gelatin was full of it in the first place.

Two honest points belong at the end. First, several of these milestones are securely documented — Braconnot's 1820 isolation from gelatin and Berzelius's 1848 naming are about as firm as nineteenth-century chemical history gets — while a few finer details (exact attributions and dates for the structural and mechanistic steps) are reported with the ordinary uncertainty of old science, and we have flagged those as estimates where appropriate. Second, knowing the history is not a health claim: that glycine was isolated two centuries ago and turns up everywhere in the body is a reason it is worth studying, not proof of any particular benefit. The thread from a pot of boiled gelatin in 1820 to the molecule we now place inside the collagen helix, at the synapse, and in the genetic code is unbroken — and following it carefully, and accurately, is the point of telling the history at all.

Back to Table of Contents

Research Papers and References

The list below combines peer-reviewed sources on glycine and amino-acid history with curated PubMed topic-search links. The earliest events in this article rest on historical primary literature — above all Henri Braconnot's own reports of the acid hydrolysis of gelatin, published in the Annales de Chimie et de Physique around 1820 — which are named here as historical sources rather than as modern citations. 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. Wang W, Wu Z, Dai Z, Yang Y, Wang J, Wu G. Glycine metabolism in animals and humans: implications for nutrition and health. Amino Acids. 2013;45(3):463-477. — doi:10.1007/s00726-013-1493-1 · PMID: 23615880
  2. Simoni RD, Hill RL, Vaughan M. The discovery of the amino acid threonine: the work of William C. Rose. Journal of Biological Chemistry. 2002;277(37):E25. — PMID: 12218068
  3. Henri Braconnot — isolation of glycine from gelatin (1820) and the early acid hydrolysis of proteins. Annales de Chimie et de Physique (historical primary literature). — Biographical overview: Henri Braconnot
  4. The Nobel Prize in Chemistry 1902 — Hermann Emil Fischer, "in recognition of the extraordinary services he has rendered by his work on sugar and purine syntheses." — NobelPrize.org: Emil Fischer
  5. Glycine — discovery, naming, and biochemistry (overview) — PubMed: glycine metabolism and health
  6. History of the amino acids and their discovery — PubMed: amino-acid discovery and essentiality

External Authoritative Resources

Back to Table of Contents

Connections

Back to Table of Contents