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Water Soluble Vitamins
aeraer
40
Biochemistry
Professional
01/14/2012

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Term
Thiamine - general
Definition
Vitamin B1

assists in the cleavage of bonds adjacent to a carbonyl group (acetaldehyde transfer)

key to the utilization of met carbon sources as energy (CAC -acetylCoA)

precursors of enzyme cofactors and nucleic acids (PPP)
Term
Thiamine unique chemistry
Definition
C-2 of Thiazolium ring is the site of attachment of the "active acetaldehyde" group

and attacking nucleophile that assists in the decarboxylation reactions

has resonance stabilization which creates an electron sink**
Term
Electron Sink
Definition
when a structure prevents the reactivity of another group from compromising the reaction with side groups
Term
Pyruvate dehydrogenase+ alpha ketoglutarate dehydrogenase
dependent on TPP
Definition
1. pyruvate dehydrogenase enzyme complex depends on Thiamine pyrophosphate to decarboxylate pyruvate on E1 and transfers acetaldehyde to E2

alpha ketoglutarate dehydrogenase has similar complex converting alpha-ketoglutarate to succinyl-CoA
Term
Beriberi Disease
Definition
deficiency in Vitamin B1

paralysis and atrophy of limbs, cardiac failure

neurological symptoms
Term
Good Sources of B1
Definition
whole grains, yeast, liver
Term
Pyridoxine- general
Definition
Vitamin B6

all aminotransferases use PLP as a prosthetic group

exhibits ping-pong kinetics

important in amino acid catabolism, CAC intermediates

sequesters toxic ammonia as glutamine
Term
Pyridoxine unique chemistry
Definition
electron sink on pyridinium ring which delocalizes a negative charge

Schiff base* resonance of intermediates
Term
B6 deficiency
Definition
rare

dermatitis and glossitis

occurs in elderly and diets with severe nut. deficincies
Term
Good sources of B6
Definition
meats, whole grain, vegetables, nuts
Term
Riboflavin- general
Definition
Vitamin B2- (FAD)

in electron transfer 1 or 2 e

in oxidative phosphorylation (CAC, E transport, FA oxid)
Term
Riboflavin unique chemistry
Definition
redox

the standard reduction potential at which they operate is dependent upon the nature of their interaction with their carrier enzyme
Term
Good Sources of Vitamin B2
Definition
asparagus, bananas, okra, chard, cottage cheese, milk, yogurt
Term
Vitamin B2 deficiency
Definition
rare

due to high affinity of flavoproteins for flavins
Term
Niacin- general
Definition
Vitamin B3 - NAD

2 electron transfers only

freely diffusible (redox pot doesn't vary)

CAC, E tra, aa oxi, glycolysis, FA oxi
Term
Niacin unique chemistry
Definition

NAD+ is for catabolic reactions

NADPH is for anabolic reactions

dehydrogenases use common motif  "Rossmann fold" to bind NAD

Term
Vitamin B3 deficiency
Definition
Pellagra

causes diarrhea, dementia, dermatitis
Term
Good sourches of B3
Definition
meat, wheat germ, dairy products and yeast
Term
Ascorbic acid- general
Definition
Vitamin C

reducing agent

is an antioxidant that keeps the non-heme iron of prolyl-4-hydoxylase in its reduced form

iron remains oxidized and proline hydroxylation activity is abolished

pathway - collagen synthesis
Term
prolyl 4- hydroxylase
Definition
alpha2,beta2 tetramer

essential for collagen stability

alpha contains 1 non-heme iron

can also decarboxylate alpha-ketoglutarate in an uncouple reaction

if Fe2+ remains oxidized after this reaction due to lack of ascorbic acid, enzyme inactive and can't hydroxylate proline

this leads to connective tissue problems
Term
Vitamin C -deficiency
Definition
scurvy

connective tissue problems
tooth loss
Term
one- carbon metabolism
Definition
involves the transfer of one-carbon fragments from one molecule to another

essential for the synthesis of nucleotides, aa and regulation of bio processes
Term
Biotin
Definition
Vitamin B7

1C metabolism

coenzyme, serves as a carrier of active CO2

CAC, gluconeogenesis (pyurvate carboxylase)
Term
Good Dietary Sources of B7
Definition
swiss, chard, tomatoes, romaine lettuce, carrots
Term
Colbalamin
Definition
Vitamin B12

1C metabolism

cofactor in enzymes where a substituted alkyl group is exchanged for a hydrogen on an adjacent C, w/o H20 accessing the H atom

FA oxid in od #, methionine synthesis
Term
Avidin or streptavidin pull-down assay
Definition
Avidin immobilized onto solid supports is also used as purification media to capture biotin labled proteins

used in western blot, ELISA
Term
Pyruvate to Oxaloacetate
Definition
CAC deficient in oxaloacetate use BIOTIN

pyruvate to oxaloacetate

allows citrate synthase to use more acetyl-CoA

pyruvate carboxylase requires acetyl-CoA for activity
Term
Vitamin B12 unique chemistry
Definition
carbon-cobalt bonds allows reversible free radical generation

only 2 b12 containing enzymes
-methylmalonyl-CoA mutase
-methionine synthase
Term
Vitamin B12 deficiency
Definition
Leads to pernicious anemia

reduced production of rbc, reduced levels of hemoglobin, progressive CNS impairment
Term
Good sources of Vitamin B12
Definition
fish, meat, poultry, eggs, milk
Term
Folic Acid- general
Definition
Vitamin B9 (THF - tetrahydrofolate)

acts as a carrier of 1C units in a variety of metabolic reactions
Term
N5,methyl -THF
Definition
not readily converted to the other forms of folate

bioavialbility is limited causing methyl-folate trap
Term
Methyl- Folate trap
Definition
Methionine synthase reaction requires B12 = ALL FOLATE must go through reaction

it is the only way to convert N5 methyl-THF to a convient form

B12 deficiency will lead to a build up of N5-methyl-THF leading to a shortage of other forms of folate and subsequent impairment in other processes
Term
uses of 1C framgents on THF
Definition
purine biosynthesis - N10-formyl-THF

Thymidylate synthase - N5, N10 methylen

Methionine Synthasis - N5- methyl-THF
Term
Sulfonamides
Definition
are analogues of p-aminobenzoic acid and inhibit dihydropteroate synthetase

which is a bacterial enzyme that synthesizes folic acid

these compounds inhibit bacterial folate synthesis are excellent antibiotics, mamals are dependent on dietary folate
Term
Good sources of Folate
Definition
Leafy vegetables
Term
Folate Deficiency
Definition
megaloblastic anemia

cant make thymidylate and purines required for growth

impaired methylation
Term
Homocystein as diagnostic target
Definition
in the blood mirrors the efficiency of 1C metabolism as a diagnostic target of a variety of disorders associated with impaired methylation
Term
Homocystein unique chemistry
Definition
reactive free thiol group

it can spontaneously form adducts with a # of important macromolecules in particular proteins

can potentially disrupt solvent-accessible disulfide bonds
Term
Negative concequeneces of impaired methylation
Definition
global hypomethylation and localized hypomethylation of DNA

impaire regulation of important genes

implicated in vascular disease and cancer

high homocystein will inhibit methylation reactions involving SAM
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