Who Discovered Peptides?

Overview

The discovery of peptides is not the work of a single person but the result of a century of converging research in organic chemistry, physiology, and biochemistry. The concept of a "peptide" as a short chain of amino acids linked by amide bonds emerged at the turn of the 20th century, largely through the work of the German chemist Emil Fischer. Fischer demonstrated that amino acids could be joined in defined sequences, coining the term "peptide" around 1902 and synthesizing the first dipeptide (glycylglycine) in the late 1890s.

Before Fischer, researchers had observed that proteins could be hydrolyzed into smaller nitrogen-rich fragments, but the chemistry of the linkage between amino acids was unclear. Theodor Curtius and Franz Hofmeister independently proposed that amino acids could be connected by amide (now called peptide) bonds. Hofmeister presented the hypothesis at a conference in 1902, almost simultaneously with Fischer, which is why both men are often credited with establishing the peptide bond concept.

The subsequent century built on this foundation, with chemists and physiologists isolating biologically active peptides such as insulin, oxytocin, vasopressin, and many hormones of the hypothalamus. Each discovery added to a growing catalog of naturally occurring peptides and deepened our understanding of how short chains of amino acids regulate virtually every physiological process.

Key People

• Emil Fischer (1852–1919): German chemist who received the 1902 Nobel Prize in Chemistry and pioneered peptide synthesis and nomenclature.
• Franz Hofmeister (1850–1922): Austrian-Czech biochemist who independently proposed the peptide bond structure.
• Theodor Curtius (1857–1928): German chemist who developed early methods for amino acid coupling.
• Frederick Sanger (1918–2013): Determined the first complete amino acid sequence of a protein (insulin) in 1955.
• Vincent du Vigneaud (1901–1978): First to synthesize a biologically active peptide hormone, oxytocin, in 1953.

Timeline

• 1820s–1830s: Early isolation of amino acids from protein hydrolysates.
• 1888: Curtius synthesizes early dipeptides using hippuric acid methods.
• 1902: Fischer and Hofmeister independently propose the peptide bond structure.
• 1901–1907: Fischer synthesizes a series of di-, tri-, and tetrapeptides.
• 1921: Discovery of insulin by Banting, Best, Macleod, and Collip.
• 1953: Du Vigneaud synthesizes oxytocin, the first peptide hormone made in the laboratory.
• 1955: Sanger publishes the full sequence of insulin.
• 1963: Solid-phase peptide synthesis is introduced by R. Bruce Merrifield.

Background

The identification of peptides depended on the broader revolution in organic chemistry that began in the mid-19th century. Once amino acids were recognized as the constituents of proteins, the question became how they were linked. Early proposals included ester linkages, iminazole rings, and diketopiperazines. Fischer's systematic synthetic work, combined with Hofmeister's physiological reasoning, settled the matter in favor of the amide (peptide) bond as the primary linkage in proteins.

The peptide concept was essential for the later development of protein chemistry, enzymology, and modern pharmacology. Without a clear understanding of how amino acids connect, the isolation, sequencing, and synthesis of biologically active peptides such as ACTH, glucagon, and calcitonin would not have been possible.

Modern Relevance

The original discovery of peptides has a direct line to today's pharmaceutical industry. The peptide drug market now includes dozens of approved molecules — from insulin analogs and GLP-1 agonists to gonadorelin analogs — all of which rely on the fundamental chemistry established more than a century ago. Modern techniques such as solid-phase synthesis, recombinant expression, and mass spectrometry would be impossible without the peptide-bond framework that Fischer and Hofmeister first articulated.

Peptide science has also expanded far beyond hormones. Therapeutic peptides now include antimicrobial agents, cell-penetrating peptides, targeted radiopharmaceuticals, and stapled peptides designed to disrupt protein-protein interactions. The discovery that amino acids link through a specific, reproducible chemistry remains foundational to every one of these innovations.

Related Compounds

• Insulin
• Oxytocin
• Vasopressin
• Glucagon
• ACTH