Knowing Peptides: Terms & Types

What is a Peptide?

A peptide is a small molecule made up of two or more amino acids linked together. These amino acids are connected by something called a peptide bond, which forms when the amino group of one amino acid links to the carboxyl group of another, releasing a water molecule in the process. The term "peptide" comes from a Greek word meaning “to digest.”

Peptides are crucial in biology and are found naturally in humans and other animals. They also have many applications in medical research and drug development, making them a hot topic in scientific studies.

How Are Peptides Formed?

Peptides can be made naturally in our bodies or artificially in the lab. Our bodies create peptides to perform specific functions, like sending signals between cells or fighting infections. Scientists can also make peptides in the lab using techniques like liquid phase peptide synthesis or solid phase peptide synthesis, the latter being the more common method today.

The first synthetic peptide was made in 1901, and since then, scientists have created many more, including some used as medications.

Types of Peptides

Peptides are categorized based on how many amino acids they contain:

  • Dipeptides: 2 amino acids
  • Tripeptides: 3 amino acids
  • Oligopeptides: Fewer than 10 amino acids
  • Polypeptides: More than 10 amino acids
  • Sometimes, larger peptides are called proteins, although there's some overlap in how these terms are used.

Peptides can also be classified by how they are made:

  • Ribosomal peptides: Made in cells by reading mRNA.
  • Nonribosomal peptides: Made by special enzymes and can have complex structures.
  • Milk peptides: Formed from the proteins in milk.

Important Terms in Peptide Science

  • Amino Acids: Building blocks of peptides.
  • Cyclic Peptides: Peptides that form a ring shape.
  • Peptide Sequence: The order of amino acids in a peptide.
  • Peptide Bond: The link between two amino acids in a peptide.
  • Peptide Mapping: A technique to identify the structure of peptides and proteins.
  • Peptide Mimetics: Molecules that mimic the biological activity of peptides.
  • Peptide Fingerprint: A pattern used to identify peptides after breaking them into smaller pieces.
  • Peptide Library: A collection of different peptides used in scientific research.