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nutr 3330 midterm > biotin and pantothenic acid > Flashcards

biotin and pantothenic acid Flashcards

1
Q

study reminder

A

be able to recognize biotin structure on an exam

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2
Q

what is free-biotin called

what is protein-bound biotin called

A
  • biotin

- biocytin

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3
Q

biotin and raw egg diet

A

avidin binds biotin tightly, causing a deficiency leading to symptoms

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4
Q

biotin is bound to ____ in foods

A

protein

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5
Q

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

A

biotinidase

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6
Q

where does the cleavage and absorption of biotin occur?

A

intestine

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7
Q

what inhibits biotin absorption

A

avidin

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8
Q

what are the metabolic functions or biotin

A
  • 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
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9
Q

list the 4 biotin dependent enzymes

A
  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

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10
Q

what is the biotin dependent enzyme pyruvate carboxylase used in

A
  • glucose metabolism
  • important step for gluconeogenesis
  • regenerates OAA for gluconeogenesis
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11
Q

what is the biotin dependent enzyme acetyl CoA carboxylase used for

A

FA synthesis

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12
Q

what is the biotin dependent enzyme propionyl CoA carboxylase used for

A

-source of energy; entry into TCA

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13
Q

what is the biotin dependent enzyme 3-methlycrotonyl used for

A

-AA metabolism; leucine degradation

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14
Q

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

A

holocarboxylase

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15
Q

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

A

holocarboxylase synthase

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

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16
Q

how could a biotin deficiency occur

A
  • decreased intake
    • -> TPN solutions without biotin: bypass the gut and go right into blood
  • dec absorption (Avidib)
  • deficiency in key enzymes (genetic defects)
17
Q

egg white injury disease

A

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

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

18
Q

what happens to avidin when it is cooked

A

it is denatured and the affinity for biotin is therefore destroyed

19
Q

what are symptoms of biotin deficiency

A

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

20
Q

holocarboxylase synthase

A

attaches biotin to lysine of caboxylase enzymes

21
Q

holocarboxylase synthase deficiency

A

in children=immunodeficiency diseases

22
Q

biochemical results of biotin deficiency

A
  • 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
23
Q

biotin food sources

A
  • liver
  • whole grain cereals
  • nuts legumes, peanut butter
  • low in fruits and vegetables
24
Q

bacterial synthesis of biotin

A

biotin can be synthesized by intestinal bacteria

25
Q

what affects biotin requirement

A
  • large amounts of raw egg white
  • biotinidase deficiency (genetic)
  • drug interactions, anticonvulsants, biotin depletion
  • pregnancy
26
Q

what are the two major coenzymes of pantothenic acid

A

Coenzyme A (CoA)

Acyl Carrier Protein (ACP)

both contains SH (thiol) group, which is where the actions of reactions happens

27
Q

what is CoA synthesized from

A

pantothenic acid
cysteine
ATP

28
Q

metabolic role of CoA

A
  • transfer of Acetyl groups (2C)
  • connect to SH groups
  • central nutrient metbolism
  • many anabolic and catabolic fates
29
Q

list 5 examples of CoA transferring acetyl groups

A
  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
30
Q

Acyl carrier protein (ACP)

A

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

31
Q

metabolic role of ACP (acyl carrier protein)

A
  • FA synthesis
    • is an enzyme complex
    • pantothenic acid is a prosthetic group of ACP
    • ACP serves as chaperone for FA synthesis
32
Q

Pantothenic acid deficiency

A

rare (since it is widespread in food)

  • ->pant=greek for every/all
  • burning feet syndrome!*
33
Q

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

A

pain in toes and soles of feet

common in:
WWII prisoners of war
poorly nourished in the Far East

34
Q

what other uses does pantothenic acid serve

A

wound treatment
-oral and topical (in rate)

cholesterol-lowering

nutr 3330 midterm (13 decks)

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