UNIT 11: MICRONUTRIENDS III: Pantothenic Acid, Biotin, Folate, VitB12, VitB6 Flashcards
What is Pantothenic acid?
aka vitamin B5
- water soluble vitamin
pantos = everwywhere
deficiency = rare
What are the forms of pantothenic acid?
- free
- bound
What is pantothenic acid converted to?
coenzyme A
What forms 4-phosphopantetheine?
What is the purpose of this?
pantothenic acid + cysteine + phosphate (ATP)
- cofactor in fatty acid synthesis
- further metabolized to coenzyme A
What is Biotin?
aka vitB7
- water soluble vitamin
Raw eggs lead to ___>
biotin deficiency (biotin binding protein with raw egg)
Biotin is found in what types of foods?
- bound to proteins
- not enough made by bacteria in humans
What is biotin’s role as an enzyme cofactor?
transfers carboxylic functional group
What are 3 reactions that involve carboxylation via biotin?
- pyruvate carboxylase (pyruvate –> oxaloacetate)
- acetylCoA carboxylase (acetylCoA –> malonylCoA)
- propionylCoA carboxylase (propprionylCoA –> methylmalonylCoA)
What is folate?
aka vitB9
- water soluble vitamin
What are sources of folate?
- folate = foliage = leafy greens
What are sources of folic acid?
supplements and enriched breads, flours, corn meals, rice noodles etc.
What is the difference between folate and folic acid?
folic acid comes from fortified/supplements –> pteroylmonoglutamates
folate comes from plants and animals –> pteroylpolyglutamates which is further broken down to pteroylmonoglutamates
Which form of folate is absorbed?
pteroylmonoglutamate
- needs to be in this form/broken down to this before absorption
- this also makes folic acid more bioavailable since folate has more steps before absorption
What is a major example of folate deficiency?
Neural Tube Defect
- neural tube forming in development, requires steady supply of folate
- deficiency can cause Spina Bifida
What is Vitamin B12?
aka cobalamin (cobalt centre) - water soluble vitamin
What is the source of vitB12?
- originally from colonic bacteria (not absorbed by colon)
- stored: liver (up to 10 years)
- animal foods: fed with vB12 diet (fecal diet) (vegans risk deficiency)
What is unique regarding vit B12 absorption?
- “intrinsic factor” chaperones B12 through GIT
- requires specific binding protein in small intestine for absorption
- receptor recognizes “intrinsic factor”-vitB12 complex
- receptor does not recognize vitB12 alone
What other vitamin is vitB12 linked to?
folate (vitB9)
VitB12 and folate are required for what process?
SAM cycle
DNA synthesis and repair
- Dietary folate caries N6-methyl group while vitB12 acts as a prosthetic gropu in methionine synthase (using N5-methylTHF)
Folate deficiency leads to what in DNA synthesis?
- low dTMP, high dUMP
= nucleotide pool imbalance - slow DNA synthesis
- dUMP incorporated in DNA when it should not be
= uracil misincorporation
–> cancer
B12 deficiency leads to:
- bone marrow impairment of DNA synthesis –> anemia
- RBC precursors cannot meet demands
- Neural tube defect same as folate
What happens if you have a high folate diet but vitB12 deficiency?
- anemia does not occur
- DNA repair and synthesis is okay
- other symptoms!
What is the toxicity of vitB12?
there is no toxicity
= no upper limit
What is vitamin B6?
water soluble vitamin
What are the forms of vitB6?
- pyridoxine
- pyridoxal
- pyridoxamine
phosphorylated and dephosphorylated = 6 forms of vit B6
What is the main form of vitB6 in the blood?
phosphorylated pyridoxal = PLP
- blood
- bound to albumin
What is the main form of vitB6 in plants?
pyridoxine
- converted to PLP
What is the major storage site of vitB6?
muscle
What are functions of vitB6
- transamination (protein metabolism)
- porphyrin synthesis (heme)
- neuroactive amines (EP/NE, serotonin, histamin, GABA)
What happens if you have vitB6 deficiency?
rare
- anemia, convulsions, neuroactive amine metabolism
What is the toxicity of vitB6?
- pain and numbness in extremities
- large TI
- difficult to achieve UL but exists
