73 by: Morgan Bohn
Student – Morgan Bohn
Name and EC of the enzyme – Thyroid Peroxidase (TPO), EC# 1.11.1.1-14.
Where to find the enzyme – Thyroid Peroxidase is an enzyme made up of 933 amino acids and its found in the follicular cells that make up follicles inside the thyroid gland. The enzyme is found in the follicular cell and has a domain in the membrane and colloid (inside the lumen).
What the enzyme does – Thyroid Peroxidase catalyzes the oxidation of iodide from the bloodstream into iodine or a reactive form of iodine. The enzyme uses H2O2 and Iodide, the hydrogen peroxide binds to a heme domain in the enzyme. The Iodide molecule is stabilized somewhere in the active site, by hydrogen bonding, Van Der Waals forces, residues like arginine or histidine (positively charged polar) may play a role in stabilization. The exact location and chemistry behind this Iodide bonding isn’t clear. The H2O2 binds to the heme and the result allows iodide to attack, resulting in reactive forms of iodine. This allows iodine to be attached to tyrosines on thyroglobulin, which are then coupled to produce thyroid hormones. Thyroid hormones are vital for metabolism and development so thyroid peroxidase is very important for many bodily functions but primarily metabolism.
Other interesting facts – The overall synthesis of thyroid hormone is well known, but the molecular part that Thyroid Peroxidase plays is less well known. I found it interesting that it can play a role in all three key parts of thyroid hormone synthesis such as oxidation, iodination, and coupling. Issues in these processes can lead to hypothyroidism, so the importance of Thyroid Peroxidase was quite interesting.
References:
Tokoph, K. (2017, April 20). Thyroid Peroxidase and Thyroid Treatments. [Catalyst University, Youtube]. Retrieved from https://www.youtube.com/watch?v=ekq_tdKEJps
(2022, March 23). Thyroid Hormone Synthesis: Step-By-Step Pathway [Physiology Explained]. [Ezmed, Youtube]. Retrieved from https://www.youtube.com/watch?v=1Dgz9Pky6WA
Pang, A. Chan, W. (2010). Molecular Basis of Diesease of the Endocrine System (chapter 22, pg 289-307). Retrieved from https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/thyroid-peroxidase
Le, S. N., Porebski, B. T., McCoey, J., Fodor, J., Riley, B., Godlewska, M., Góra, M., Czarnocka, B., Banga, J. P., Hoke, D. E., Kass, I., & Buckle, A. M. (2015). Modelling of Thyroid Peroxidase Reveals Insights into Its Enzyme Function and Autoantigenicity. PloS one, 10(12), e0142615. https://pubmed.ncbi.nlm.nih.gov/26623656/
Audio Reference:
(Note: Parody’s are considered fair use so not violating copyright)
Sing, K. (2023, July 29). Vanilla Ice – Ice Ice Baby (Karaoke Version). [Sing King, Youtube] Retrieved from https://www.youtube.com/watch?v=CmER6_swceY
