biotin and pantothenic acid

Question 1

study reminder

Answer 1

be able to recognize biotin structure on an exam

Question 2

what is free-biotin called

what is protein-bound biotin called

Answer 2

• biotin

- biocytin

Question 3

biotin and raw egg diet

Answer 3

avidin binds biotin tightly, causing a deficiency leading to symptoms

Question 4

biotin is bound to ____ in foods

Answer 4

protein

Question 5

what is the name of the enzyme that cleaves biocytin to biotin plus lysine

Answer 5

biotinidase

Question 6

where does the cleavage and absorption of biotin occur?

Answer 6

intestine

Question 7

what inhibits biotin absorption

Answer 7

avidin

Question 8

what are the metabolic functions or biotin

Answer 8

• functions as part of coenzyme for carboxylases
• serves as CO2 donor to substrates
• CO2 fixation reactions
• 4 unique enzymes that depend on biotin..all involved in macronutrient and energy metabolism

Question 9

list the 4 biotin dependent enzymes

Answer 9

1. pyruvate carboxylase
2. acetyl CoA carboxylase
3. propionyl CoA carboxylase
4. 3-methylcrotonyl CoA carboxylase

see OH for pathways
these all end in carboxylase so only need to remember first part

Question 10

what is the biotin dependent enzyme pyruvate carboxylase used in

Answer 10

• glucose metabolism
• important step for gluconeogenesis
• regenerates OAA for gluconeogenesis

Question 11

what is the biotin dependent enzyme acetyl CoA carboxylase used for

Answer 11

FA synthesis

Question 12

what is the biotin dependent enzyme propionyl CoA carboxylase used for

Answer 12

-source of energy; entry into TCA

Question 13

what is the biotin dependent enzyme 3-methlycrotonyl used for

Answer 13

-AA metabolism; leucine degradation

Question 14

what is the general term used to describe biotin-dependent enzymes

Answer 14

holocarboxylase

Question 15

with all co-enzymes, there must be attachment to the enzyme. What is needed to attach biotin to the lysine residue of the enzyme

Answer 15

holocarboxylase synthase

once biotin is attached to the enzyme, the enzyme is classified as a holocarboxylase

Question 16

how could a biotin deficiency occur

Answer 16

• decreased intake
  
  • -> TPN solutions without biotin: bypass the gut and go right into blood
• dec absorption (Avidib)
• deficiency in key enzymes (genetic defects)

Question 17

egg white injury disease

Answer 17

once biotin-avidin complex forms, it is irreversible, and excreted in feces, preventing absorption

this causes deficiencies in animals (depression hallucinations, muscle pain, dermatitis)

Question 18

what happens to avidin when it is cooked

Answer 18

it is denatured and the affinity for biotin is therefore destroyed

Question 19

what are symptoms of biotin deficiency

Answer 19

neurological problems (depression, lethargy, hallucinations, paresthesia of extremeties)
thinning of hair
rash

Question 20

holocarboxylase synthase

Answer 20

attaches biotin to lysine of caboxylase enzymes

Question 21

holocarboxylase synthase deficiency

Answer 21

in children=immunodeficiency diseases

Question 22

biochemical results of biotin deficiency

Answer 22

• dec in biotin-dependent enzymes
  
  • dec gluconeogenesis
  • inc pyruvate and lactate
  • less glucose produced
• dec Acetyl CoA carboxylase
  
  • build up of acetyl CoA…risk of ketosis
  • impaired serum lipids

Question 23

biotin food sources

Answer 23

• liver
• whole grain cereals
• nuts legumes, peanut butter
• low in fruits and vegetables

Question 24

bacterial synthesis of biotin

Answer 24

biotin can be synthesized by intestinal bacteria

Question 25

what affects biotin requirement

Answer 25

- large amounts of raw egg white - biotinidase deficiency (genetic) - drug interactions, anticonvulsants, biotin depletion - pregnancy

Question 26

what are the two major coenzymes of pantothenic acid

Answer 26

Coenzyme A (CoA) Acyl Carrier Protein (ACP) both contains SH (thiol) group, which is where the actions of reactions happens

Question 27

what is CoA synthesized from

Answer 27

pantothenic acid cysteine ATP

Question 28

metabolic role of CoA

Answer 28

- transfer of Acetyl groups (2C) - connect to SH groups - central nutrient metbolism - many anabolic and catabolic fates

Question 29

list 5 examples of CoA transferring acetyl groups

Answer 29

1. oxidative carboxylation - pyruvate-->acetyl CoA 2. FA oxidation - complete degradation of acetyl CoA 3. ketone body formation 4. other carboxylic reactions - AA catabolism 5. synthetic reactions - cholesterol synthesis

Question 30

Acyl carrier protein (ACP)

Answer 30

another coenzyme form of pantothenic acid, also has a reactive SH group from cysteine

Question 31

metabolic role of ACP (acyl carrier protein)

Answer 31

- FA synthesis - is an enzyme complex - pantothenic acid is a prosthetic group of ACP - ACP serves as chaperone for FA synthesis

Question 32

Pantothenic acid deficiency

Answer 32

rare (since it is widespread in food) - ->pant=greek for every/all - burning feet syndrome!*

Question 33

what is burning feed syndrome and what deficiency is it caused by

Answer 33

pain in toes and soles of feet common in: WWII prisoners of war poorly nourished in the Far East

Question 34

what other uses does pantothenic acid serve

Answer 34

wound treatment -oral and topical (in rate) cholesterol-lowering