Plasma Proteins: Definition, Structure, Functions

Plasma proteins are the collection of intricate molecules found in blood plasma. Their roles are many and varied, and they are mostly synthesized by the liver. Albumin, globulins, and fibrinogen are the three most important plasma proteins.

These proteins carry out a number of tasks, including regulating the blood’s osmotic pressure, transporting hormones and other chemicals, and assisting in the formation of blood clots. The definition, purposes, obligations, activities, advantages, and disadvantages of plasma proteins will all be covered in this article.

Complex molecules called plasma proteins are present in blood plasma. Mostly produced by the liver, they are then released into the blood plasma. Albumin, globulins, and fibrinogen are the three primary classes into which they are divided. Each group performs and possesses some unique characteristics.

Table of Contents

Interesting Science Videos

Structure of Plasma Proteins

Depending on the kind of protein, plasma proteins have different structures. Unlike globulins, which are more complicated and may include numerous chains of amino acids, albumin is a straightforward protein made up of a single chain of amino acids. The complex protein fibrinogen is made up of alpha, beta, and gamma chains, among others. The capacity of plasma proteins to attach to other molecules and take part in numerous physiological processes is determined by their structure, which is crucial for their function.

Categories of Plasma Proteins

A variety of intricate molecules called plasma proteins can be discovered in the blood plasma. The three primary categories are albumin, globulins, and fibrinogen.

Albumin

Making up around 60% of all the protein in the blood, albumin is the most prevalent form of plasma protein.
It is a simple protein made up of just one amino acid chain. Albumin is essential for preserving the blood’s osmotic pressure, which is required to maintain the body’s electrolyte and water balance.
Additionally, it aids in the transportation of numerous molecules such as fatty acids, hormones, and enzymes.

Globulins

Alpha, beta, and gamma globulins are only a few of the many subtypes of globins, a class of proteins that are more complicated than albumin.

Alpha Globulins – The group of proteins known as alpha globulins includes the alpha-fetoprotein, which is generated by the foetal liver and is utilised as a marker for certain cancers. Alpha-1-antitrypsin, which aids in lung damage prevention, and alpha-2-macroglobulin, which aids in immune response regulation, are other alpha globulins.
Beta globulins – Beta globulins include a variety of proteins, including complement proteins and transferrin, which aid in the movement of iron throughout the body.
Immunoglobulins, commonly referred to as gamma globulins, are essential for the immunological response. They are produced by B cells and help protect the body against infections.

Fibrinogen

Fibrinogen is a complex protein that is involved in the blood clotting process. It is synthesized by the liver and is converted to fibrin during the clotting process. Fibrin helps to form a clot, which is necessary to stop bleeding after an injury.

In addition to these three main types of plasma proteins, there are also a number of other proteins that are found in smaller quantities in the blood plasma, including lipoproteins, which transport lipids throughout the body, and enzymes, which catalyze biochemical reactions.

Plasma Protein Functions

Many different processes are carried out by plasma proteins, including:

Blood osmotic pressure maintenance – Albumin is the primary protein that aids in blood osmotic pressure maintenance. This pressure is required to maintain the body’s electrolyte and water balance.
The maintenance of the body’s general health depends on plasma proteins. They assist in controlling the body’s water balance, moving crucial chemicals around the body, and guarding the body against infections.
For instance, albumin maintains the blood’s osmotic pressure, which helps to avoid the buildup of extra fluid in the tissues.
Transportation – Hormones and other molecules are transported by globulins and albumin, which also aid in the movement of enzymes and other molecules.
Blood Clot Formation – The primary protein that aids in the formation of blood clots is fibrinogen. In order to stop excessive bleeding after an injury, they are also essential for the blood clotting process.
Immunity – Some globulins, including immunoglobulins, participate in the immunological response and aid in defending the body against infections.

Plasma Proteins Development Process

The genes in the liver cells play a major role in controlling the production and regulation of plasma proteins. More than 90% of plasma proteins are made in the liver, and a sophisticated web of genetic pathways controls how they are made. A variety of elements, including hormones, nutrition, and illness, can affect how the genes that code for plasma proteins are expressed.

Scientists are still learning more about the roles of plasma proteins and how they may be used in medicine. The use of plasma proteins in the creation of novel treatments for a variety of diseases, such as cancer and autoimmune disorders, has gained popularity in recent years. Additionally, new techniques for producing plasma proteins have been developed as a result of biotechnology advancements, including the use of recombinant DNA technology.

Advantages and Drawbacks

Advantages – One benefit of plasma proteins is that they are essential for preserving the body’s general health. They aid in maintaining the proper balance of water in the body, carry vital molecules across the body, and guard against infections. Plasma proteins are also employed in a number of medical procedures, such as the therapy of the immune system and blood problems.

Drawbacks – However, there are some drawbacks to plasma proteins as well. For instance, the blood’s plasma protein levels may become unbalanced in illnesses like liver or renal disease, which might affect one’s health. Additionally, some people may have an allergic reaction to plasma proteins, which can cause symptoms such as hives, itching, and difficulty breathing.

Genetic Control and Application

Research into the particular genes and processes involved in the production and control of these significant molecules is underway in the domain of the genetic control of plasma proteins. New pathways for modifying the genetic regulation of plasma proteins and creating novel therapies for a variety of medical illnesses may be opened up by technological advancements like gene editing and gene therapy. The study of plasma protein structure is another important topic of research, with researchers employing a variety of methods, including X-ray crystallography and NMR spectroscopy, to comprehend how these intricate molecules are put together and performed in the body.

Sequential Changes in Plasma Proteins After Surgery

Plasma proteins play a crucial role in the body’s response to surgery, as they are involved in inflammation, tissue repair, and immune function. The levels and composition of plasma proteins can change in response to surgery, and understanding these changes can provide important insights into the body’s response to surgical trauma.

The sequential changes in plasma proteins after surgery can be divided into three phases: the acute phase response, the resolution phase, and the late phase response.

Acute Phase Response

C-reactive protein, serum amyloid A, and fibrinogen levels all quickly rise as part of the acute phase response, which is the body’s initial reaction to surgical trauma. These proteins aid in mobilizing the body’s immune response to the site of damage and are involved in tissue healing and inflammation. After surgery, the acute phase reaction normally lasts a few days.

Resolution and Late Phase

The resolution phase is characterized by a reduction in the levels of acute phase proteins and an increase in the levels of proteins involved in tissue repair, such as albumin and transferrin.
The resolution phase is a time when inflammation is waning.
This period, which might persist for a number of weeks following surgery, is crucial for healing and tissue generation.
After surgery, there may be a protracted period of changed plasma protein levels called the “late phase response,” which might extend for several months.
The levels of certain growth factors that are involved in tissue remodeling and scar formation, such as transforming growth factor beta, rise during this period.

Generally speaking, the adjustments in plasma proteins following surgery reflect the body’s reaction to the trauma as well as the process of tissue regeneration and repair. Understanding these alterations can offer crucial insights into how the body reacts to surgical stress and could point to fresh treatment targets for the promotion of recovery and reduction of postoperative problems.

Depletion of Abundant Plasma Proteins and Limitations of Plasma Proteomics

The goal of the quickly developing field of study known as plasma proteomics is to identify and count the proteins found in blood plasma.

The presence of extremely abundant proteins, which might prevent the identification of important proteins with low abundance, is one of the main difficulties in plasma proteomics.
Prior to doing a proteomic analysis, researchers frequently employ depletion techniques to take out the most prevalent proteins from plasma.
It entails the careful removal of the sample’s most prevalent proteins, sometimes with the use of antibodies or other affinity-based techniques.
This can broaden the analysis’s dynamic range and enhance the identification of proteins with lower abundances.
However, this strategy has a number of drawbacks. Depletion strategies may not completely eliminate all highly abundant proteins, even though they can remove a sizable fraction of them.
This may cause lingering interference with the identification of proteins with lower abundances.

Information Loss

Depletion techniques may eliminate proteins that are important to answering a particular research issue, as well as extremely abundant proteins. For instance, certain depletion techniques can eliminate specific cytokines, growth factors, or other bioactive molecules that are scarcely present yet have significant biological functions.

Sample Variability

Plasma proteomics is highly dependent on the quality and consistency of the sample, and depletion methods can introduce additional variability. Differences in sample handling, storage, or preparation can affect the efficiency of depletion, leading to variability between samples.

Technical Limitations

Some depletion methods may not be compatible with certain downstream proteomic techniques or may introduce artifacts that affect the accuracy and reproducibility of the analysis.

Conclusion

Important macromolecules known as plasma proteins are involved in a number of physiological processes, such as immune response, inflammation, and tissue repair. Proteomics has been actively researching the characterization of plasma proteins and how they alter in response to various stressors, such as surgery. Researchers frequently employ depletion techniques to get around this constraint since the presence of very abundant plasma proteins might hinder the identification of low-abundance proteins. Although depletion techniques can increase the dynamic range of proteomic analysis, they have drawbacks as well, such as incomplete depletion, information loss, sample variability, and technical constraints. In order to obtain reliable and repeatable findings, it is crucial to carefully consider the possible advantages and limits of depletion approaches while planning proteomic studies. Further innovations in sample preparation, depletion strategies, and bioinformatic analysis are necessary to advance the field of plasma proteomics and uncover new insights into the role of plasma proteins in health and disease.

References

Putnam, Frank, ed. The plasma proteins V3: structure, function, and genetic control. Elsevier, 2012.
Tu, Chengjian, et al. “Depletion of abundant plasma proteins and limitations of plasma proteomics.” Journal of proteome research 9.10 (2010): 4982-4991.
Aronsen, K-F., et al. “Sequential changes of plasma proteins after surgical trauma.” Scandinavian Journal of Clinical and Laboratory Investigation 29.sup124 (1972): 127-136.
Rodríguez‐Martínez, Heriberto, et al. “Seminal plasma proteins: what role do they play?.” American journal of reproductive immunology 66 (2011): 11-22.