Zinc (Part 2)

Question 1

What are the functions of zinc?

Answer 1

Catalytic, structural, regulatory

Question 2

What is carbonic anhydrase?

Answer 2

First characterized zinc metalloenzyme

Question 3

What does carbonic anhydrase do?

Answer 3

Interconverts carbon dioxide and bicarbonate to maintain acid-base balance in blood

Question 4

What is the rxn of carbonic anhydrase?

Answer 4

CO2 +H20 -> H2CO3 (bicarbonate)

Question 5

In carbonic anhydrase, zinc is coordinated by what?

Answer 5

3 histidine residues

Question 6

What are examples of Zn catalytic functions?

Answer 6

Metalloenzymes:

• Alcohol dehydrogenase
• RNA polymerase
• Alkaline phosphatase
• carbonic anhydrase
• carboxypeptidase A

Question 7

What is carboxypeptidase?

Answer 7

A digestive enzyme produced by the pancreas

Question 8

What does carboxypeptidase do?

Answer 8

Hydrolyzes peptide bonds

Question 9

In carboxypeptidase, zinc is coordinated by what?

Answer 9

2 histidine and 1 glutamic acid residue

Question 10

For carboxypeptidase, the R’ group can be any AA except?

Answer 10

Arg, Pro, Lys, and hydroxyproline

Question 11

Why does the pancreas cause the body to lose a lot of zinc?

Answer 11

Because these digestive enzymes are secreted from the pancreas and a lot of them contain zinc.

Question 12

What is an example of a structural zinc function?

Answer 12

Zn binding proteins

Question 13

What is an example of a zinc binding protein?

Answer 13

Superoxide Dismutase 1

Question 14

What is superoxide dismutase 1?

Answer 14

An antioxidant enzyme

Question 15

What does Superoxide Dismutase 1 do?

Answer 15

It catalyzes the “dismutation” of superoxide, converting it to hydrogen peroxide

Question 16

What is the role of Cu in superoxide dismutase 1?

Answer 16

Serves a catalytic role in electron transfer during dismutation rxn

Question 17

What is the role of Zn in superoxide dismutase 1?

Answer 17

Serves a structural role

Question 18

What is the most common DNA binding domain?

Answer 18

Zinc finger domain

Question 19

What are two different forms of mammalian zinc fingers?

Answer 19

C4 (4 Cysteine residues): Nuclear receptors and C2H2 (2 Cysteine and 2 Histidine residues) family

Question 20

What are examples of C4: Nuclear receptors?

Answer 20

Retinoic Acid Receptor (RAR) and Vitamin D receptor (VDR)

Question 21

Why do proteins have zinc finger domains?

Answer 21

It allows proteins to bind to DNA which may activate or inhibit the expression of genes.

Question 22

Zinc Status assessment

Answer 22

Plasma zinc <70micrograms/dL

Question 23

Why is Plasma Zn not a very good indicator?

Answer 23

Because it is affected by many factors such as stress, meal, time of the day, infection, medications

Question 24

What is an example of genetic zn deficiency?

Answer 24

AE (Acrodermatitis enteropathica)

Question 25

Who was the first person to document Zn deficiency?

Answer 25

Ananda Prasad

Question 26

When was Zn declared to be an essential nutrient in the U.S.?

Answer 26

1974

Question 27

Why is the skin on the cheeks affected by AE so much?

Answer 27

Because the skin on the cheeks is one of the fastest turning over pieces of skin on your face and have the highest zinc demand.

Question 28

Where is Zn deficiency prevalence high?

Answer 28

Africa, Asia

Question 29

Loss of life of children under the age of 5 is due to?

Answer 29

Vit. A def, Zn def, and Iron def.

Question 30

Vitamin A and Zn account for how much of childhood disability-adjusted-life-years

Answer 30

9%

Question 31

What is the RDA for Zn?

Answer 31

~10 mg

Question 32

Zn toxcity

Answer 32

Does not exist because body can excrete excess zinc

Question 33

Symptoms of toxicity can exist if

Answer 33

200 mg of zinc is taken

Question 34

What are the symptoms of Zn toxicity?

Answer 34

Nausea, vomiting, epigastric pain, abdominal cramps, bloody diarrhea

Question 35

Chronic ingestion of Zn (~40 mg/day) can cause what?

Answer 35

Cu def

Question 36

Penny case: why were his zn levels high?

Answer 36

Because he ingested post 1982 pennies which are mainly made of zinc and they were partially digested causing increase in zinc levels