Zinc (Part1) Flashcards
Where is zinc mainly found?
Shellfish, beef
How is Zinc absorbed?
Mainly in the small intestine
- Carrier-mediated which is saturable. It is separated into two parts, the apical and basolateral membrane transport
- Passive which is non-saturable by parracellular diffusion
How is Zinc absorption regulated?
Increased dietary zinc = decrease absorption = increase fecal loss
How is zinc homeostasis mainly regulated?
By how much you absorbed
What proteins are involved in Zinc absorption and transport in the intestine?
Zip4 = uptake ZnT1 = transport
ZnT1 knockout mice do not exist because…
It is embryonic lethal
What is Acrodermatitis enteropathica (AE)?
A disease of zinc malabsorption Zinc -responsive inborn error of metabolism Symptoms include -dermatitis -impaired immunity -impaired wound healing -hair loss -anorexia - impaired taste acuity
AE is caused by?
A mutation in Zip4
Who does AE mainly affect?
Young infants
How do you treat AE?
Providing 20-30 mg Zn supps/ Day
What enhances Zinc absorption?
Amino Acids such as histidine, methionine, cysteine
Organic acids such as citrate
What are inhibitors of Zinc absorption?>
Phytate and Iron
How is Zinc transported in the plasma?
Mainly bound to albumin in circulation
There are a few tissues that take up more zinc than others such as…?
The pancreas
Why does the pancreas take up a lot of zinc
?
Because the insulin producing B-cells take up a lot of zinc because they need zinc to make and secrete insulin
Besides absorption and excretion how else can zinc be regulated?
By the pancreas excretions of bile
How is Zinc excreted?
Mainly fecal
but in diseases of muscle catabolism urinary excretion may increase
What are the Zip proteins?
Importers
What are the ZnT proteins?
Exporters
Why are there so many Zinc transporters?
Because they are expressed in different tissues
How much zinc is stored and where is most of it located?
Total zinc content is 1.5-2.5g and the skeletal muscle holds most of it.
What is metallothionein?
A zinc storage protein and Copper storage
How many AA does MT have and how many of those are cystienes?
61 and 20 are Cysteines
How many atoms of Zinc /copper can bind to MT for storage?
7
What are the functions of Zinc?
- Catalytic
- greater than 300 known Zn metalloenzymes - Structural
- Zinc finger proteins - Regulatory
- Zinc finger proteins
Zn Metalloenzymes
Alkaline phosphatase, RNA polymerases, Alcohol dehydrogenase
