Biotin Flashcards
biotin foods
ALL FOODS
liver, beef
food form of biotin
free or covalently bound to proteins like biocytin
small amount of biotin is produced by __ in __
small amount of biotin is produced by bacteria in colon
SMVT aka
shared multivitamin transporter
biotin transporter
SMVT
SMVT is inhibited by
excess biotin
SMVT is a
Na-depdent symporter
biotin enters cell from
intestinal lumen (mainly jejunum)
biotin is found mostly __ in __ with small amounts bound to __, __, and __
biotin is found mostly free in plasma with small amounts bound to albumin, globulins, and biotinidase
biotin uptake in __ and other cells is likely mediated by __ carrier and __
biotin uptake in liver and other cells is likely mediated by SMVT carrier and monocarboxylate transporter (MCT)
biotin is present in small amounts in
brain
liver
muscle
biotin has __ and __ functions
biotin has coenzyme and non coenzyme functions
4 coenzyme functions of biotin
- pyruvate carboxylase
- acetyl CoA carboxylase
- propionyl CoA carboxylase
- beta-methylcrotonyl CoA carboxylase
1 nonenzyme function of biotin
regulation of gene expression
the enzyme __ covalently attaches __ groups to target proteins (__ and __)
the enzyme holocarboxylase synthetase (HCS) covalently attaches biotin groups to target proteins (enzymes and histones)
HCS deficiency
within hours to weeks of birth
emesis, hypotonia, lethargy, metabolic ketolactic acidosis
similar diagnosis to HCS (they are often confused)
biotinidase deficiency (appears after 3 months)
2 non-coenzyme roles of biotin
- biotinylation of proteins and gene regulation
- cell cycle
biotinylation of proteins and gene regulation (3)
- histones: biotinylation opens up DNA-histones
- over 2,000 genes depend on biotin expression
- non-histone proteins are also targets for biotinylation
biotinidase function
recycles biotin to be used by the body
biotin is an essential coenzyme for 5 __
biotin is an essential coenzyme for 5 carboxylases
what vitamin is involved in carboxylase activity?
biotin
biotin in cell cycle
required for progression
biotin deficiency causes cell arrest in G1 phase
the biotin cycle
- biotin enters from diet
- HCS helps biotin find and bind targets (holocarboxylases)
- once active, holocarboxylases participate in protein, lipid, and carb metabolism
- once used, holocarboxylases are degraded
- biocytin remains after degradation
- biotinidase releases biotin for next round of activation
biotin is essential in __, __, and __ metabolism
biotin is essential in protein, lipid, and carb metabolism
excretion metabolites produces from __ of __
via __
excretion metabolites produced from oxidation of valeric acid
via urine, some in feces
assessment of biotin status (2)
- plasma and urinary biotin
- urinary excretion of 3-hydroxy-isovaleric acid
is biotin deficiency common?
no, very rare but lethal if untreated
groups at risk for deficiency
alcohol addiction
diets high in raw eggs
genetic mutations (biotinidase)
groups at risk for deficiency
alcohol addiction
diets high in raw eggs
genetic mutations (biotinidase)
biotin deficiency symptoms
neurologic: lethargy, depression, hallucinations
skin abnormalities: dermatitis around eyes, mouth, and eyes
how to treat biotin deficiency
free biotin daily
all biotin are attached to a
lysine
biotinidase is present
everywhere!
SMVT requires what to transport biotin into cell
Na
biotin cycle: HCS binds to __ and biotinylates them making other enzymes biologically active
biotin cycle: HCS binds to histones and biotinylates them making other enzymes biologically active
biotin is mainly secreted as an __ product
biotin is mainly secreted as an oxidized product
