What is the Difference Between Prealbumin and Albumin

The key difference between prealbumin and albumin is that prealbumin is a transport protein in the plasma and cerebrospinal fluid and transports thyroid hormone and retinol to the liver, while albumin is a transport protein in the serum and helps to move many small molecules including bilirubin, calcium, progesterone, and medicines through the blood.

Transport proteins are proteins that serve the function of moving other materials within an organism. They are very important to the growth and the life of all living things. There are several different types of transport proteins, and prealbumin and albumin are two of them.

CONTENTS

1. Overview and Key Difference
2. What is Prealbumin 
3. What is Albumin
4. Similarities – Prealbumin and Albumin
5. Prealbumin vs Albumin in Tabular Form
6. Summary – Prealbumin vs Albumin

What is Prealbumin?

Prealbumin is a transport protein in the plasma and cerebrospinal fluid that transports thyroid hormone (T4) and retinol to the liver. It is also known as transthyretin. Prealbumin is encoded by the TTR gene located on the 18^th chromosome. Prealbumin is known as transthyretin because of its function – transporting thyroxine and retinol. The liver secretes prealbumin to the blood. However, the choroid plexus secretes TTR into the cerebrospinal fluid. In agarose gel electrophoresis, prealbumin runs faster than albumin. Other than thyroxine and retinol, many other small molecules like natural products (resveratrol), drugs (tafamidis, vyndaqel, diflunisal, and flufenamic acid), and toxicants (PCB) can bind to prealbumin.

Structurally, prealbumin is a 55 kDa homotetramer. In addition to the liver and choroid plexus, it can also be synthesized in the retinal pigment epithelium. Therefore, it can be present in the eye as well. Moreover, prealbumin misfolding and aggregation are normally associated with amyloid diseases such as wild-type transthyretin amyloidosis, hereditary transthyretin amyloidosis, familial amyloid polyneuropathy, and familial amyloid cardiomyopathy. Prealbumin has been shown to interact with perlecan, which is a key component of the extracellular matrix of cartilage. Furthermore, prealbumin testing is normally done to investigate conditions like malnutrition. This is because when people experience nutrient deficiency, prealbumin levels tend to go down.

What is Albumin?

Albumin is a transport protein in the serum that helps to move many small molecules, including bilirubin, calcium, progesterone, and medicines, through the blood. Albumin is a protein made by the liver. The serum albumin test usually measures the amount of this protein in the clear liquid portion of the blood. Albumin can also be measured in the urine. The protein of albumin family is water soluble. They are moderately soluble in concentrated salt solutions. Moreover, albumin also undergoes heat denaturation.

The prime function of albumin is to regulate the oncotic pressure of blood. It also carries water, cations such as Ca²⁺, Na⁺ and K⁺, fatty acids, hormones, bilirubin thyroxines, Wnt proteins, and vitamin E. Moreover, it can also regulate bone mineralization. Albumin is a 65 kDa to 70 kDa protein. Furthermore, a low level of albumin is associated with different health conditions such as chronic illness or infection, malnutrition, liver disease, kidney disease, protein-losing enteropathy, heart failure, severe burns, pregnancy, and some genetic disorders.

What are the Similarities Between Prealbumin and Albumin?

• Prealbumin and albumin are two types of transport proteins.
• Both are made up of amino acids.
• Both are found in the serum.
• They play vital functions in the body.
• Deregulation of both proteins leads to diseases.

What is the Difference Between Prealbumin and Albumin?

Prealbumin is a transport protein that transports thyroid hormone and retinol to the liver, while albumin is a transport protein that helps to move many small molecules, including bilirubin, calcium, progesterone, and medicines, through the blood. Thus, this is the key difference between prealbumin and albumin. Furthermore, the molecular weight of prealbumin is 55 kDa, while the molecular weight of albumin is around 65 to 70 kDa.

The below infographic presents the differences between prealbumin and albumin in tabular form for side-by-side comparison.

Summary – Prealbumin vs Albumin

Prealbumin and albumin are two types of transport proteins. Prealbumin is a transport protein involved in the transport of thyroid hormone and retinol to the liver, while albumin is a transport protein involved in the movement of many small molecules, including bilirubin, calcium, progesterone, and medicines through the blood. So, this summarizes the difference between prealbumin and albumin.

Reference:

1. “Prealbumin.” An Overview | ScienceDirect Topics.
2. “Albumin.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.

Image Courtesy:

1. “Prealbumin Dimer ribbon” By Jane Richardson – Own work (CC BY 3.0) via Commons Wikimedia
2. “Albumin hemin complex“ (CC BY 2.0) via Commons Wikimedia