Zinc Flashcards
ZnTs
Moves zinc out of cells.
** ZIP14 **
Out of blood into liver
Located on hepatocytes, upregulated during infection.
Removes zinc from blood and away from infective organisms that can use it.
Defense mechanism.
Up regulation can indicate infection.
Liver.
ZIP4
Inversely related to zinc status.
Zinc absorption low = more ZIP4 (enhances absorption)
Mutation causes malabsorption syndrome.
ZIP5
Transfer to enterocyte
Can reabsorb zinc back into enterocyte.
Reabsorbs zinc if there’s too much in circulation.
Sloughs off cells to get rid of zinc.
Enterocyte.
** ZnT6 **
Transfer to lumen
Recycles zinc from enterocyte to the lumen to be excreted. Active.
Lumen.
Purposeful elimination.
** ZnT1 **
Out of cells into blood
Transports zinc out of cells.
Tissue cells.
ZIPs
Moves zinc into cells.
Sources
Red meats, oysters, fortified cereals.
20-30% bioavailability.
Supplementation on empty stomach.
RDA
11mg men
8 mg women
Double for vegetarians (decreased bioavailability in plant foods due to non heme iron)
Higher absorption probably (low zinc status)
Assessment
Serum
Function
Component of ~200 metalloenzymes.
Structural integrity more so than functional.
Binds to AA at catalytic sites.
Zinc fingers
Solid, stable structure for proteins. Many functions.
Can curl along DNA strands to read DNA sequences.
** Metalloenzyme component: Ligase and Lyase **
Catalyzes the joining of 2 large molecules.
Bond forming.
Catalyzes the breaking of various bonds.
Zinc in development/ growth
Regulates gene expression and cell replication.
Can result in poor growth in children if deficient because cells don’t grow fast enough.
Retardation and skeletal growth impaired.
Zinc and infections
Structural role in hormones (thymulin - immunity)
Retionol to retinal conversion (RBP synthesis retinonol binding protein)
Zinc and taste
Taste acuity.
Zinc required for gustin synthesis.
Gustin is zinc-containing protein in saliva.
Deficiency symptoms
Growth retardation, skeletal abnormalities, and delayed sexual maturation in children. Zn used in cell division and DNA replication.
Infection (thymulin and retinal conversion)
Skin lesions (cell growth)
Loss of taste (hypogeusia) [gustin]
Toxicity
UL 40mg/ day
Also creates copper deficiency (zinc binds to metallothionine better than copper)
Protein carriers that transfer zinc through blood
60% albumin
Transferrin, immunoglobulin, and the AA’s cysteine and histidine.
Zinc storage
Metallothionine stores zinc in tissues.
Liver stores zinc when it’s not being transferred.
Albumin contains 60% of Zn in blood
Enhancers
Acids: low pH, HCl, citric acid, AA.
Zinc is usually bound to proteins, which acids break away.
Inhibitors
Non heme iron, calcium, antacids, tannins, phytates, oxalate.
Excrete zinc instead of absorb.
Thionein
Upregulated when zinc levels are high.
Binds to zinc to form metallothionine.
Gustin
Zinc dependent protein used for taste
Transport
Transferred through the blood bound to protein carriers:
Albumin, Transferrin, Immunoglobulins, etc.
AA: histidine and cysteine
ZIP1
Transport to tissue cells
Brings zinc out of blood into cell.
Can either be stored, used as a cofactor, or ego to nucleus to upregulate thionine to bind to something.
Metallothionine
Directly correlated to Zn status. Bind to Zn.
More Zn = more metallothionine
How can zinc be recycled?
Enterohepatic circulation
Supplement
Should be taken on empty stomach.
Excretion
GI tract in feces
Zn bound to metallothionine lost in cell sloughing
ZIP5 and ZnT6 purposeful elimination (GI)
Zinc and Growth
Gene expression
Cell replication
Zinc and Immune Function
Structural role in hormone thymulin which is part of immune system.
Retinol to retinal conversion. RBP synthesis.
Retinal binding protein
Acrodermatitis Enteropathica
Mutation in ZIP4 causes Zn malabsorption.
Nigh blindness (VA), impaired wound healing, skin rashes, chronic diarrhea, swelling of corneas.
Treatment is Zn supplementation to absorb passively.
Thymulin
Hormone in immune system that needs zinc.
Protects against infection.
