Distribution of selenium-containing proteins in human serum

Area of Science:

• Biochemistry
• Analytical Chemistry
• Human Physiology

Background:

• Selenium is an essential trace element crucial for human health, functioning primarily through selenoproteins.
• Understanding the distribution and quantification of selenium-binding proteins in human serum is vital for assessing selenium status and related health implications.

Purpose of the Study:

• To separate, purify, and quantify selenium-containing proteins in human serum.
• To identify and characterize the major serum selenium-binding proteins and their relative abundance.

Main Methods:

• Preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for protein separation.
• Microwave digestion and 2,3-diaminonaphthalene (DAN) derivatization for selenium quantification.
• High-performance liquid chromatography coupled with a fluorescence detector (HPLC-FLD) for sensitive selenium detection.

Main Results:

• Five distinct selenium-containing proteins with molecular weights of 68±3, 57.5±2.5, 47±2, 41±1, and 21±1 kDa were identified.
• The 68 kDa protein is likely albumin (6.3-9.8% of total serum Se).
• Selenoprotein P (57.5 kDa) and its 47 kDa isoform constitute the major fraction (41.1-69.3%) of serum selenium.
• Plasma glutathione peroxidase (p-GPx, 21 kDa) accounted for 21.1-24.3% of serum selenium.
• A novel 41 kDa selenium-containing protein was identified, representing 12.6-20.4% of total serum selenium.

Conclusions:

• Human serum contains at least five distinct selenium-binding proteins.
• Selenoprotein P and its isoform are the predominant forms of selenium in human serum.
• A previously unreported selenium-containing protein of 41 kDa was identified, highlighting the complexity of serum selenium distribution.