Enzyme of the month January edition - Alanine Aminotransferase (ALT)
The enzyme I would like to introduce you to in January is a liver enzyme called Alanine Aminotransferase. It is a very crucial enzyme in cellular respiration. The purpose of cellular respiration is to produce energy in the form of a chemical molecule known as ATP. Many biochemical pathways are involved in cellular respiration. Examples of animal cellular energy pathways include Glycolysis1 and Tricarboxylic Acid Cycle (TCA)2.
Cellular respiration is a very neat and detailed process that breaks down the food molecules we ingest. The chemical reaction for cellular respiration is:
C6 + H12 → 6 CO2 + 6 H2O
Where does the enzyme
ALT fall into this complex process? ALT contributes towards the functioning of
the TCA cycle. We will now discuss how ALT carries out its important function
in cellular respiration.
A very important thing to remember is that the goal of
cellular respiration is to create chemical energy to be utilized by the body. Cellular respiration
produces intermediates of the molecule that ultimately produce ATP3.
Specifically, the production of the chemical molecules NADH4,
Hydrogen and GTP5 take place in the TCA cycle of cellular
respiration. These molecules later engage in the synthesis of ATP when needed
by the body. There is an intermediary process that follows glycolysis and takes
place before the TCA cycle. In this process, the pyruvate molecule produced in
glycolysis is converted to Acetyl-CoA. The complete oxidation of Acetyl-CoA7
in the TCA cycle leads to the production of NADH, H, and GTP.
It is now time to
discuss where the enzyme ALT falls into cellular metabolism. ALT is involved in
the metabolism of amino acids (proteins). Through this process, the protein
sources are broken down for the body to convert them into forms of energy. ALT,
specifically, converts the amino acid Alanine to Pyruvate. Then as discussed
earlier, the pyruvate6 molecule is essential for producing the
energy molecule, ATP.
As I mentioned earlier,
ALT is a liver enzyme that participates in protein digestion. Because it is a
liver enzyme, ALT is considered to be an indicator of liver health. ALT enzymes
are stored in the liver itself. A very little amount of this enzyme is found
in the other parts of the body like muscles, kidney, brain, and heart (Patrick, 2020). In a healthy body, ALT enzyme
levels in the bloodstream are quite low. According to Medicine Net, the normal
ALT level in units per liter of serum is 7 to 56 (Patrick,
2020). Therefore, liver disease can be evident if there is an abnormally high level of ALT in the bloodstream. However, high levels of ALT do
not immediately suggest liver disease. There can be numerous factors that lead to
elevated ALT levels. Hence, consulting with a doctor when the ALT levels are
abnormally high is advised.
I hope this blog helps
you understand the role of the enzyme ALT! Stay tuned for the enzyme of the
month in February
2. Follows the process of glycolysis where the
glucose molecules are oxidized to produce water and carbon dioxide which serve
as waste products of the metabolic pathways
3. An adenosine molecule packed with three phosphate molecules that
repel each other. When the phosphate molecules are released, a lot of energy is
produced to be used by the body for various functions.
4. A coenzyme that helps in producing energy from the food molecules. Plays a crucial role in oxidation-reduction reactions of cellular metabolism by
donating or accepting Hydrogen.
Alanine Aminotransferase
- an overview | ScienceDirect Topics. (2017). Sciencedirect.com. https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/alanine-aminotransferase
A Glimpse at The function of NADH and FADH2 in Cellular Respiration. (2015, April 4).
Biology Wise. https://biologywise.com/function-of-nadh-fadh2
BD Editors. (2017,
January 27). Pyruvate. Biology Dictionary. https://biologydictionary.net/pyruvate/
5 Major Metabolic
Pathways in Organisms| Microbiology. (2016, November 28). Biology Discussion. https://www.biologydiscussion.com/metabolism/microbial-metabolism/5-major-metabolic-pathways-in-organisms-microbiology/65509
Guanosine Triphosphate -
an overview | ScienceDirect Topics. (2013). Sciencedirect.com. https://www.sciencedirect.com/topics/medicine-and-dentistry/guanosine-triphosphate
Knapp, S. (2020,
December 6). Alanine Aminotransferase. Biology Dictionary. https://biologydictionary.net/alanine-aminotransferase/
Patrick, C. (2020, June 22). Liver Blood Tests (Normal, Low, and High Ranges
& Results). MedicineNet;
MedicineNet. https://www.medicinenet.com/liver_blood_tests/article.htm
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