Question | Answer |
Lecture 49 | Water Soluble Vitamins II |
Active form of pyridoxine is ___. | pyridoxine phosphate |
Manifestations of pyridoxine deficiency are: | irritability, depression, neuropathy, and convulsions |
Pyridoxine deficiency symptoms arise from interference of ___ synthesis. | neurotransmitter |
B6 dependent synthesis processes are: | dopamine/norepinephrine/epinephrine, serotonin/melatonin, GABA |
B6 dependent step in synthesis of dopamine, norepinephrine, and epinephrine is ___. | DOPA decarboxylase |
B6 dependent step in synthesis of GABA is ___ | glutamate decarboxylase |
Pyridoxine responsive anemia is caused by defective ___. | ALAS2 (gene coding for an aminolevulinic acid synthase) |
AST/SGOT | Catalyzes the reversible transamination of L-aspartate and α-ketoglutarate to oxaloacetate and L-glutamate |
High prevalence of low B6 in young women was assessed by ___. | tryptophan load test |
Tryptophan load test measures ___ in the urine, the B6 dependent step. | kynurenine |
Activation Coefficient | [Activity after B6] / [Activity before B6] |
Normal activation coefficient is ___. | stable (goes up only a small amount after supplement) |
Abnormal activation coefficient has a ___ coefficient. | high (drastically increased activity after supplement) |
Folic acid is a ___ donor. | methyl |
Tetrahydrofolate is a ___ carrier. | 1-carbon |
Methylene Tetrahydrofolate Reductase | Catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetradehydrofolate |
Formation of cysteine from homocysteine is a ___ dependent step. | vitamin b12 |
Folate deficiency causes: | inadequate intake, impaired absorption (alcoholism, GI disease), impaired metabolism (B12 deficiency, methotrexate), increased requirement (lactation, pregnancy, neural tube defects), anticonvulsants/OCP, |
Vitamin B12 Structure | Cobalamin (corrin ring with central cobalt), deoxyadenosylcobalamin, methylcobalamin |
Binding of B12 to ___ is essential for absorption in the ___. | intrinsic factor, distal ileum |
Pernicious Anemia | Megaloblastic anemia, fatal degeneration of spinal cord, treated with EF from liver |
B12 binds to ___. | R protein |
___ digests R, releasing B12 for binding to IF. | Pancreatic proteases |
The B12 enzymes are: | MMCoA mutase and methionine synthase |
Methionine Synthase | Catalyzes the formation of methyl B12 from hydroxy B12 |
MMCoA Mutase deficiency leads to ___. | methylmalonic aciduria |
Folate and B12 deficiency both cause ___. | megaloblastic anemia |
Folate Trap Hypothesis | Folate is trapped in the N5-MTHF form if B12 deficient, unable to regenerate tetrahydrofolate |
Folate treatment without B12 treatment can ___ or ___ B12 neurologic damage. | precipitate or mask |
The only source of cobalamin are foods of ___ origin. | animal |
Strict vegan diets will eventually lead to ___ deficiency, but takes years (10-12). | B12 |
Gulonolactone Oxidase | Catalyzes the synthesis of ascorbic acid from gulonolactone |
Vitamin C (ascorbic acid) is an ___ vitamin in humans, derived from ___ sources. | essential, exogenous |
Ascorbate is important in: | collagen biosynthesis, tyrosine degradation, epinephrine/carnitine synthesis, bile acid synthesis, iron absorption, bone mineral metabolism, antioxidant |
Scurvy | Vitamin C deficiency, failure in matrix and collagen, heavily mineralized bones, bleeding underneath the bone (“bone-in-a-bone”) |
Ecchymosis, purpura, and petechia are ___, most likely due to ___ synthesis. | sub-dermal bleedings, collagen |