Zinc Flashcards
What are the best foods sources of zinc?
Oysters
Crabmeat
Shrimp
Tuna
Mostly animal products: meats and seafood
The functions of zinc are categorized into what 3 areas?
- Structural
- Catalytic
- Regulatory
What are the structural roles of ZINC?
a) Metalloenzymes
b) Zinc fingers
Metalloenzymes
proteins containing metal ions, so zinc binds to this and helps provide structure
Usually zinc that can help with the binding of very complex proteins
Zinc fingers
A small protein structural motif (secondary structures) that is characterized by the coordination of one or more zinc ions, in order to stabilize the fold
Binds to DNA, RNA, and proteins
3% of 32,000 genes in humans
Many acts as transcription factors, regulating 3% of the genes in humans
What are the catalytic functions of zinc?
Zinc acts as a cofactor, in a number of enzymatic reactions, as a catalyst.
a) Protein and carbohydrate metabolism (many enzymes require zinc)
b) Nucleic acid metabolism
What are the regulatory functions of zinc?
a) Transcription Factors (Zinc stimulates MTF-1 dependent transcription)
b) Cell Signaling
Explain the function of zinc as a transcription factor.
Zinc interacts with metal transcription factor (MTF-1) in the cytoplasm; dimerizes, translocates into the nucleus, and binds to MREs to induce expression
**Important in modulating growth, cell differentiation, and expression of mRNA with translation into proteins.
MTF-1
Metal Transcription Factor 1
MTF-1 knockouts are lethal so the number of genes regulated by them is unclear.
Explain the function of zinc in cell signaling.
Zinc can function not only to regulate the expression of mRNA, but also as a regulatory mechanism, as part of cell signaling.
CELL MOVEMENT
CT, BONE, TOOTH DEVELOPMENT
SYSTEMIC GROWTH, ENDOCRINE REGULATION
CYTOKINE PRODUCTION
IMMUNE RESPONSE
Where is zinc found in the body?
Muscle (~60%)
Bone (~30%)
Liver
Kidney
Hair
Kidney
Explain zinc absorption.
Zinc is brought into the enterocyte via ZIP4 TRANSPORTER and leaves via ZnT1 TRANSPORTER
It will enter circulation, bound to albumin or another globin-type protein
Where do we see zinc losses?
In the feces, 2 different mechanisms are:
1) Liver and pancreas will secrete bile and enzymes into the SI to help with digestion and absorption. Zinc will be excreted through the pancreatic enzymes, bile acid, and bile salts
2) Zinc can be kept in the enterocyte and stored here temporarily (similar to IRON), and zinc will be lost when the enterocytes turnover every 4-5 days.
Where was zinc deficiency first discovered?
Iran and Egypt
What are the risk factors for zinc deficiency?
Low dietary intake
Increased need (children)
Malabsorption (Crohns, IBS)
Increased losses (Alcoholism)
Impaired utilization (DM, infection, inflammation)
