Peptide VS Protein: How Do They Differ?

Peptide vs protein — the only difference is their size. But scientists have been focusing on peptide breakthroughs. Find out why below.

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Comparing Peptide Vs Protein: Knowing Their Differences

What Are Peptides?

Simply put, peptides are smaller proteins composed of 2-50 amino acids. But scientists have drawn sub-terminologies from it for more specific referencing:

  • Polypeptide – peptides containing 10 or more amino acids
  • Cyclotide – peptides that comprise 28-37 amino acids forming a circle. These are typically used in peptide-based drugs formulated for microbes and tumors.

What Are Proteins?

Structurally speaking, proteins are large peptide molecules comprised of 100 or more amino acids. Scientists may also refer to them as complex polypeptides.

One good example of a protein is hemoglobin, the part of red blood cells which carries oxygen throughout the body. It’s comprised of four chains of amino acids, two of which have 146 amino acids each and the other two have 141 amino acids each.

Peptides vs Proteins in Medical Research

Both types of peptide proteins mimic the behavior of a ligand—this is the main reason they have been receiving a lot of attention in the clinical laboratories.

Ligand Definition: Substances that function to respond to an enzyme’s or cell’s receptor to trigger biological processes

But peptides are preferred by clinicians. This is because they carry promising therapeutic benefits which include:

  • Since their behaviors are similar, they provide fewer side effects compared to other small-molecule drugs.
  • Peptides are generally safe even when broken down. The results are amino acids, which are, technically, food.
  • The structure of peptides allows them to be easily chemically synthesized for drug formulation.

This doesn’t mean proteins pose no health benefits at all.

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Clinical Applications of Proteins

Proteins have a promising application as antibodies. In treating cancer, for example, there are various antibodies used in clinics: Humira (adalimumab) for autoimmune diseases like rheumatoid arthritis and Herceptin (trastuzumab) for breast cancer.

Proteins are used for drug applications for the same reason as peptides—they copy something natural or replace something damaged or missing in the human body.

The Potential of Peptide-Based Drugs


Cyclotides don’t have loose ends that can cause their fast degradation. They are more stable because of their interlocking cross-links.

Their compact and stable structure allows them to reach their target without the risk of breaking, even if people consume them orally.

There are two promising cyclopeptide-based antibiotics currently being studied. One of these is glycopeptide-enhanced Vancomycin.

This antibiotic formulation aims to target bacterial cells more selectively. It uses Vancomycin as its core to solely target bacterial cells and excluding mammalian or human cells.

The second one involves cyclic lipopeptide-enhanced antibiotics that target hard-to-kill Gram-negative bacteria.

Injectable Peptides

Subcutaneous and intravenous peptides are also slowly becoming popular. An example is a peptide-based drug used in treating type 2 diabetes—Exenatide (Byetta), which uses a synthetic peptide from the Gila monster’s venom.

Agricultural Peptides

The speedy structural break down of peptides makes them good ingredients in fungicides and insecticides. They don’t stay in the environment for too long—they can help the crops and degrade by themselves.

The Challenge on Creating Peptide-Based Drugs

The body processes peptides naturally and easily since they are innate in it and are structurally easy to break down. As an answer, drug developers are trying to mimic peptides by creating small molecules replicas which are more stable inside the body.

But it’s hard to copy peptides. Dosage and formulation remain struggles for professionals.

Utilizing peptides and proteins for healthcare demands an understanding of their structure and makeup. Both have great potentials in the therapeutic industry but scientists need more research and tests to make them completely effective and functional for use.

It may take some time to figure things out, but drug developers are on their way to making these protein-based and peptide-based drugs dominant in their use.

What do you find interesting about peptides and proteins? Share your thoughts in the comments section below!

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