Biotin and Pantothenic Acid Flashcards
coenzyme function of biotin
adds CO2 as bicarbonate
biotin bound lysine is called
biocytin and is difficult to digest
foods containing biotin need what for digestion
biotinidase
why do we need biotinidase in the body
remove biotin from lysine for reuse
biocytin -> biotin + lysine = take the biotin and add to protein
biotin’s role as a non coenzyme
regulate gene expression
4 biotin enzymes
carboxylases
1. pyruvate carboxylase
2. acetyl CoA carboxylase
3. propionyl-CoA carboxylase
4. leucine catabolism enzyme
pyruvate carboxylase function
convert pyruvate (3 carbons) to oxaloacetate (4 carbons)
to replenish citric acid cycle intermediates
acetyl CoA carboxylase function
acetyl CoA (2 carbons) to malonyl CoA (3 carbons)
needs initial CO2 added to acetyl CoA
synthesize fatty acids
propionyl-CoA carboxylase
Entry of Odd Chain FAs into TCA Cycle
Propionyl-CoA + CO2 (biotin coenzyme w/in) ➜D-methylmalonyl-CoA [D-MM-CoA]
Next: D-MM-CoA -> Succinyl-CoA using
5’-deoxyadenosyl cobalamin (B12)
need 3 vitamins: pantothenic, biotin, B12
leucine catabolism enzyme
important for energy production
Food sources of biotin
whole grains, meat and alt, dairy, egg yolk
= harder to meat biotin needs if following a low cholesterol diet
not added in any specific fortification
significant GI/ microbial synthesis of biotin we can absorb and use- setting EAR difficult
DRI biotin # and how was it set
unable to set EAR
intestinal synthesis of 1/2 of our needs
little deficiency unless eating raw eggs
AI = 30mcg, similar to healthy pop
set by extrapolating up from infant AI (human milk content of biotin)
NO UL
biotin deficiency cause
rare- raw egg whites bc protein avidin tightly binds biotin and prevent absorption
In-born errors of metabolism for biotin – one type is a defective biotidinase for biotin recycling, so child needs a lot of free biotin for rest of life - rare
biotin deficiency symptoms
affects brain (symptoms include hallucinations, lethargy); eventually lethal to infants alopecia and anorexia
pantothenic acid coenzyme forms
- Coenzyme A (CoA)
4’phosphopantatheine (piece of CoA) in Acyl carrier protein (ACP)
function of CoA binding to short and long chain fa from acetate (2Carbons) to DHA (22 carbons)
central to energy-producing reactions because of acetyl CoA Citric acid cycle intermediates
ACP transfers acyl groups to extend fa chain
how does CoA bind to fa ester
via SH binding site, thio ester
energy function of CoA
pyruvate dehydrogenase complex
pyruvate -> acetyl CoA = key reaction for energy release
Acetyl CoA is entry to citric acid cycle, building block for fa, cholesterol, aa
non-energy function of acetyl CoA
acetylation of molecules (protein, sugar)
acetyl + choline = acetylcholine
drug metab (activate, inactivate molecules)
acetylation/deacetylation of histones
ACP needed for
to add 2-carbons units to fatty acids to make it a chain
ACP: small protein + pantetheine
DRI for pantothenic acid
AI= 5mg
based on average intake of US pop
thought to maintain balance
not commonly assessed- urine excretion < 1mg/day indicates poor status
maybe added to breakfast cereals (canada)
pantothenic acid deficiency
no specific disease
rarely occurs naturally in humans
“burning feet syndrome’ of POWs in Hong Kong = starvation + forced labour + multiple deficiencies
could occur in chronic diseases associated with poor diets or poor absorption (alcohol, IBS)
UL pantothenic acid
none, no known adverse effects
