what is the cofactor/coenzyme for of biotin?
CoA
what are the coenzyme biochemical functions of biotin (B7)?
- carrier of activated CO2 in carboxylation reactions (pyruvate carboxylase)
what are the free form biochemical functions of biotin (B7)?
- gene expression
- cell cycle regulation
- skin/hair health
what are the key enzymes involved with biotin?
- pyruvate carboxylase
- acetyl-CoA carboxylase
- propionyl-CoA carboxylase
- b-methylcrotonyl-CoA carboxylases
- holocarboxylase
what physiological processes is Biotin found in?
- gluconeogenesis
- fatty acid synthesis
- branched-chain aa catabolism
what are common biotin deficiences?
- rare, neurological symptoms due to biotinidase deficiency
- hair loss, brittle nails
what are common dietary sources of biotin?
eggs, nuts, liver, avocados
what processes can help biotin be absorbed in the small intestine?
passive diffusion or sodium-dependent transport
what three structures make up the free form of Biotin (B7)?
- ureido ring
- thiophene ring
- valeric acid side chain
where is biotin synthesized?
by intestinal bacteria within colon
what structures make up Biocytin?
biotin and lysine
what happens before the coenzyme form of biotin is absorbed (before it is hydrolyzed to free form via biotinidase)?
protein- or peptide-bound biotin is released via digestion by proteases or peptidases
how is free biotin transported after absorption in the jejunum and ileum of the small intestine?
travels in the blood to be up taken into tissue via sodium-dependent multivitamin transporter (SMVT)
some is stored in small qualities in the liver, muscle and brain
what is the initial and rate-limiting reaction for fatty acid synthesis?
malonyl CoA
what is the treatment of biotin deficiency holocarboxylase synthase?
large dose of biotin (40-100mg/day)
with the genetic defect in biotinidase, what are common treatment plans?
newborn screening and biotin supplements of 5-10mg daily
impaired biotin absorption can happen when ingesting what?
excess raw eggs (avidin)
what specific protein is found in egg whites that tightly bind to biotin?
avidin
