Vitamins: Biochemistry FEU-NRMF
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MARI-ANN BENIGNO-BRINGAS, MD Assistant Professor Department of Biochemistry and Nutrition FEU-NRMF Institute of Medicine VITAMINS: Chemistry and Beyond
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Transcript of Vitamins: Biochemistry FEU-NRMF
MARI-ANN BENIGNO-BRINGAS, MD
Assistant Professor
Department of Biochemistry and Nutrition
FEU-NRMF Institute of Medicine
VITAMINS:Chemistry and Beyond
VITAMINSDefinition I Function
Chemically unrelated organic
nutrients
Classified by their biological and
chemical activity and not by their
structure
Cannot be synthesized in
sufficient quantities
In natural food
Used in many chemical
reactions in the body
Unlike organic food, they do not enter into tissue
structures nor are they converted to
energy
Unlike hormones which are
endogenous, they are exogenous
VITAMINSDefinition I Function
• What vitamins are not:
– Pep pills
– Substitute for carbohydrate, fats and proteins
– Not components of cell structures
Vitamins are diverse but act similar with hormones in regulating cellular metabolism
VITAMINSCLASSIFICATION
VITAMINSDefinition I Function
Characteristics FAT-SOLUBLE VITAMINS WATER-SOLUBLE VITAMINS
Polarity
Absorption
Storage
Transport
Deficiency- prone or not
Toxicity- prone or not
Excretion
VITAMINSDefinition I Function
FAT-SOLUBLE VITAMINS WATER-SOLUBLE VITAMINS
Apolar or hydrophobic Polar
Require normal fat absorption Does not require normal fat absorption
Stored in the liver or adipose tissue No stable storage form (except vitamin B-12)
Transported in the blood by lipoproteins or specific binding proteins
Does not need protein transporters
Less prone to deficiency More prone to deficiency manifestations
Prone to toxicity Less prone to toxicity
Excreted thru feces Excreted mainly thru urine
THIAMINE B1Chemistry
THIAMINE B1Chemistry
• Methylated pyrimidine ring bonded thru a methylene linkage to a thiazole ring
THIAMINE B1Definition
• Anti-neuritic vitamin
• Anti-beriberi vitamin
• Anuerin
• Co-enzyme form:– Thiamine pyrophosphate (TPP)
– Thiamine co-carboxylase
– Thiamine diphosphate
THIAMINE B1Definition
http://www.slideshare.net/namarta28/thiamine
THIAMINE B1Properties
THIAMINE B1Metabolic Role
• Energy-releasing
• Has a central role in carbohydrate metabolism
• Half-life is 9-18 days• Sources:
– Meat/fish
– Beans, Nuts, Yeast
– What flour, unpolished rice
– Liver, meat, eggs
THIAMINE B1Metabolic Roles
• Co-enzyme in the decarboxylation of:
PyruvateAlpha-
ketoglutarate
Keto acids from branch-chain amino acids
THIAMINE B1Metabolic Roles
• Co-enzyme in the transketolase reactions
– RBC transketolase in most commonly used in measuring thaimine status in the body
THIAMINE B1Metabolic Roles
• Thiamine triphosphate (TTP)
nerve tissue metabolism and
conduction
Synthesis of neurotransmitters
(Ach)
Regulates nerve-impulse
transmission
THIAMINE B1Metabolic Roles
Central role of thiamine diphosphate
w
THIAMINE B1Metabolic Roles
THIAMINE B1Metabolic Roles
THIAMINE B1Metabolic Roles
TPP
TPP
THIAMINE B1Deficiency
May occur in the following conditions:
When the energy intake is mostly from
rice
Ingestion of foods containing anti-
thiamine factors.
Pregnancy and Lactation
Persons who do hard physical labor
THIAMINE B1Deficiency
4 Types of Beriberi
Dry
(peripheral neuritis)
Wet (cardiac manifestations)
Cerebral
(Wernicke-Korsakoffsyndrome)
Infantile
THIAMINE B1Deficiency
Dry Beriberi
Loss of appetite
Weight loss
Muscle-wasting
Peripheral neuritis with numbness
Tingling sensations in the lower legs and feet
Ataxic gait
THIAMINE B1Deficiency
Wet Beriberi
Vasodilatation, tachycardia, wide pulse pressure, sweating , warm skin
lactic acidosis
Heart Failure
Orthopnea Pulmonary and peripheral edema
Vaasodilatation
Shock
THIAMINE B1Deficiency
Cerebral Beriberi
Occurs in alcoholics who consume less food
Intelligence disturbance
Ataxia
Double vision
Nystagmus
Progresses to Wernicke-Korsakoff psychosis
THIAMINE B1Deficiency
Soshin Beriberi
More rapid form of wet beriberi
Acute fulminant CV beriberi
Cyanosis of hands and feet, tachycardia, distended neck veins, anxiety
Rapid deterioration follows inability of heart muscle to satisfy body’s demands because of its own injury
THIAMINE B1Deficiency
THIAMINE B1Deficiency
Infantile Beriberi
Due to low thiamine content of breast milk
Anorexia
Trachycardia
Vomiting
Convulsions
Edema
THIAMINE B1Deficiency
Beriberi
TYPE OF BERIBERI COMMON SYMPTOMS/FINDINGS
Neuropsychiatric Hallucinations, aggressive behavior, confusion, nystagmus, ataxia, ophthalmoplegia
Dry - Neurologic Numbness, muscle weakness, pain in the lower > uppper extremities (stocking-glove distribution) convulsions, exaggerated tendon reflexes
Wet - High output CVD Tachycardia, respiratory distress, leg edema, right ventricular dilation, lactic acidosis
Gastrointestinal Nausea, emesis, megajejunum, constipation, megacolon, atony
Source: Medscape Nat Rev Gastorenerol hepatol 2010 nature Publishing
RIBOFLAVIN B2Definition I Function
• Synonyms :
– Vitamin B2, Vitamin G, Lactoflavin
• Chemistry:– Consists of heterocyclic isoalloxazine ring attached
to a sugar alcohol, robitol
RIBOFLAVIN B2Definition I Function
• Co-enzyme forms:
– FMN Flavin mononucleotide
– FAD Flavin adenine dinucleotide
RIBOFLAVIN B2Properties
• Colored, flourescent pigment
• Widely used as food additive
• Heat stable but decomposes in the presence of visible light
RIBOFLAVIN B2Definition I Function
• RDA :
– Adults: 2.0 mg/day
– Children: 1.2 mg/day
– Pregnant/lactating: 2.0 mg/day
• Sources:
– Milk - 1 quart = 1.7 mg
RIBOFLAVIN B2Physiologic Roles
• Act as prosthetic group of flavoproteins
• Act as co-enzyme for hydrogen transfer
RIBOFLAVIN B2Metabolic Roles
• Flavoproteins:
– Enzymes involved in oxidation – reduction reactions
– FAD is required as coenzyme for:
Pyruvate dehydrogenase Carbohydrate breakdown
Succinate dehydrogenase Krebs cycle
Glycerol 3-phosphate dehydrogenase
Triglyceride synthesisphospholipid synthesis
Acyl-CoA dehydrogenase Fatty acid breakdown
Glutathione reductase Anti-oxidation
RIBOFLAVIN B2Metabolic Roles
• Flavoproteins:
– Enzymes involved in oxidation – reduction reactions
– FMN is required for:
• L-amino acid oxidase
• Cytochrome C reductase
REACTIONS WHERE FAD IS NEEDED AS COENZYME
Substrate Enzyme Product
Hypoxanthine + O2 + H2O Xanthine Oxidase Xanthine + H2O2
Xanthine + O2 + H2O Xanthine Oxidase Urate + H2O2
Succinate Succinate DH Fumarate
Glycerophosphate Glycerophosphate DH Dihydroxyacetone-PO4
Flavoproteins in electron transport chain
Glutathione reductase – for assaying riboflavin status
Part of pyruvate dehydrogenase and alpha-ketoglutaratedehydrogenase complexes
RIBOFLAVIN B2Metabolic Roles
FAD
FAD
FAD
FAD
• Causes:– Malnutrition
– Malabsorption
– Anorexia
– Chronic alcoholism
• Assay for Riboflavin status:
– Erythrocyte GSH reductase activity
RIBOFLAVIN B2Deficiency
• Ariboflavinosis
• Manifestations:
– Epithelial changes in the oral cavity• Cheilosis or perleche – fissuring of lips
• Glossitis- Magenta tongue
– Corneal Vascularization
– Seborrheic Dermatitis
– Photophobia
RIBOFLAVIN B2Deficiency
• Angular stomatitis
• A
RIBOFLAVIN B2Deficiency
• Glossitis
RIBOFLAVIN B2Deficiency
NIACIN B3Definition I Function
• Not strictly a vitamin
• SYNONYMS
– Vitamin B3, Nicotinic acid, PP factor
– Nicotinamide, niacinamide
• CO-ENZYME FORMS
– Oxidized = NAD and NADP
– Reduced= NADH AND NADPH
NIACIN B3Definition I Function
• Sources:
– Tryptophan can be converted to NAD
– 60mg Trp = 1 mg niacin
– Milk and eggs rich in tryptophan
NIACIN B3Definition I Function
• RDA:
– Adults: 16-20 mg/day
– Children: 9-16 mg/day
– Infants: 5-8 mg/day
NIACIN B3Coenzymes
NIACIN B3Coenzymes
Examples of Reactions Utilizing NAD and NADP
Substrate Enzyme Product
Lactate Lactate DH
Pyruvate
MalateMalate DH
Oxaloacetate
HydroxybutyrateBeta-OH- butyrate DH
Acetoacetate
GlucoseGlucose DH
Gluconate
IsocitrateIsocitrate DH
Alpha-ketoglutarate
GlutamateGlutamate DH
Alpha-ketoglutarate + Ammonia
NAD
NAD
NAD
NAD
NAD
NAD
NADNAD
NAD
NIACIN B3Deficiency
• CLINICAL EFFECTS:
Pellagra “rough skin” – 3D’s– Dermatitis –skin exposed to sunlight
• Casal’s necklace
• Gloves and stockings lesions
– Diarrhea
– Dementia
– Stomatitis, magenta tongue
– Severe cases, GIT hemorrhagic
* ineffective repair and regeneration of epithelial cells
NIACIN B3Deficiency
Dermatitis of Pellagra
Casal’s Necklace
NIACIN B3Deficiency
Dermatitis of Pellagra
Gloves and stocking appearance
NIACIN B3Excess
Toxicity
• 1-6 grams ( hyperlipidemia)
• Dilatation of blood vessels
• Flushing
• Skin irritation
• Liver damage
PYRIDOXINE B6Definition I Function
• FUNCTION
– Precursor of pyridoxal phosphate
– Coenzyme for several enzymes for AMINO ACID METABOLISM
• DEFICIENCY
– Intake of Isoniazid
PYRIDOXINE B6Definition I Function
• SYNONYMS:– Amino acid metabolism vitamin
– Rat anti-dermatitis factor
– Adermin
– Rat anti-pellagra factor
– Vitamin H
– Rat acrodyna factor
• CO-ENZYME FORMS:
– Pyridoxal phosphate and pyridoxinaminephosphate
– Major excretory product: 4-Pyridoxic acid
PYRIDOXINE B6Definition I Function
• Sources:– Whole grain & legumes
– Poultry & Fish
– Potatoes
– Organ meats
– Eggs
• RDA:– Adults: 2.2 mg/day
– Children: 1.2 mg/day
– Infants: 3.0 mg/day
PYRIDOXINE B6Food Sources
• RDA: Roughly proportional to the protein content of the diet
– 0.02 mg/g of protein intake
– 1.5-2.0 mg/day for normal adult
– Increased during pregnancy and lactation
PYRIDOXINE B6Definition I Function
PYRIDOXINE B6Definition I Function
PYRIDOXINE B6Definition I Function
• Physiological importance:
– Amino acid metabolism
– Synthesis of ceramide
– Synthesis of the neurotransmitters
serotonin, dopamine, epinephrine,
norepinephrine & GABA.
– Synthesis of the histamine.
– Synthesis of porphyrins
– Glycogenolysis - phosphorylase
PYRIDOXINE B6Definition I Function
• Co-enzyme in protein metabolism– Decarboxylation
– Conversion of 3-hydroxykynurenine to 3-OH-anthranilic acid
– Conversion of Tryptophan to serotonin
– Deamination – serine and threonine
– Transamination – acts as an amino group carrier
PYRIDOXINE B6Definition I Function
PYRIDOXINE B6Definition I Function
• Co-enzyme in protein metabolism– Trans-sulfuration
• transfer of sulfur from methionine to serine to form cysteine
– Conversion of cysteine to pyruvate
• via cysteine desulfhydrase
– Interconversion of glycine and serine
– Decarboxylation of alpha-amino-beta-ketoadipic acid to delta-aminolevulinic acid
PYRIDOXINE B6Definition I Function
• Co-enzyme in carbohydrate and fat metabolism
– Conversion of Linoleic to Arachidonic acid
– Cofactor in the activity of phosphorylase
– Cofactor in the metabolism of unsaturated fatty acids and cholesterol
– Synthesis of sphingolipids necessary for myelin formation
PYRIDOXINE B6Definition I Function
• Enzymes :
Amino transferases amino acid breakdown
Glycogen phosphorylase glycogen breakdown
Serine dehydratase feeding serine's breakdown product to gluconeogenesis
Aminolevulinic acid synthase
porphyrin synthesis
PYRIDOXINE B6Definition I Function
• Essential for the maintenance of the integrity of :
– Neuronal tissues
– Production of anti-bodies
– Bone development
PLP
PLP
PLP
PLP
PYRIDOXINE B6Deficiency
• Clinical features:
– Epileptiform seizures in infants
– Pellagra-like skin lesions
– GIT involvement- distention, vomiting , diarrhea
– Anemia- hypochromic and microcytic
– Acrodynia – in rats
PYRIDOXINE B6Biochemistry
• Important biochemical finding in Vitamin B6 deficiency:– Increased excretion of urinary oxalates
– Mechanism:
decreased conversion of glycine glyoxalate broken down to oxalic acid increased possibility of forming oxalate stones
• Most widely used assessment method: – Activation of erythrocyte aminotransferases by pyridoxal phosphate
added invitro, expressed as activation coefficient.
PANTOTHENIC ACIDDefinition
• SYNONYMS:
– “everywhere vitamin”
– Filtrate factor
• ROYAL JELLY
PANTOTHENIC ACIDFunction
• FUNCTION
– Component of Coenzyme A
• RDA:
– Adults: 5-10 mg/day
– Children: 4-5 mg/day
– Infants: 1-2 mg/day
PANTOTHENIC ACIDFunction
Substrate Enzyme Product
Pyruvate + CoASHPyruvate DH complex
Acetyl CoA
α-ketoglutarate- CoASHAlpha-KG DH complex
Succinyl CoA
Fattyl acid + CoASHThiokinase
Acetyl-CoA
Ketoacyl CoA + CoASHThiolase
Acyl CoA + Acetyl CoA
Detoxification of benzoic acid
Synthesis of bile salts
PANTOTHENIC ACIDFunction
• As Acetyl CoA
Combines with oxaloacetic acid to form citric acid –
first step in the Kreb’s cycle
Combines with choline to form acetylcholine
Combines with sulfonamide drugs to facilitate their
excretion
Precursor of cholesterol / steroid
hormones
Activation of some amino acids :
valine, leucine and isoleucine
Essential function in lipid metabolism
PANTOTHENIC ACIDFunction
• As Succiny CoA
– Involved in heme biosynthesis
• As Acyl Carrier Protein
– Involved in fatty acid biosynthesis
– Extra-mitochondrial lipogenesis
Acetyl CoA
PANTOTHENIC ACIDDeficiency
• Rare because:– Very widespread in natural foods
– Most symptoms are vague and mimic those of other B vitamin deficiencies
BIOTIN B7Definition
• SYNONYMS:
– Vitamin B7; anti-egg white injury factor
• CHARACTERISTICS:
– Widely distributed in natural foods
– From synthesis of bacteria - deficiency is caused by defects in utilization and not dietary
– Long-term antibiotic treatment or excessive consumption of raw egg
BIOTIN B7Definition
• AVIDIN – a protein in raw egg white which combines very tightly with biotin, preventing its absorption
BIOTIN B7Function
• FUNCTION
– Coenzymes for carboxylation reactions
– Carrier of activated carbon dioxide
• FOOD SOURCES
– Almost all foods, liver, milk, egg yolk
– 400 µg/day
• DEFICIENCY
– Uncommon
– Raw egg avidin prevents absorption of Biotin
BIOTIN B7
CARBOXYLATION REACTIONS:
BIOTIN B7Function
Substrate Enzyme Product
Acetyl CoAacetyl CoA
carboxylase
Malonyl CoA
Propionyl CoAPropionyl CoAcarboxylase
MethylmalonylCoA
Pyruvatepyruvate
carboxylase
Oxaloacetic acid
Biotin
Biotin
• Man (rare)– Fine scaly skin desquamation
– Anorexia
– Nausea
– Lassitude
– Muscle pains
– Depression/hallucination
– Alopecia
– Graying of hair
BIOTIN B7Deficiency
BIOTIN B7Deficiency
In rats
- “spectacle-eyed” appearance
- “Kangaroo posture”
- retarded growth
- loss of hair
- loss of muscular control
FOLIC ACID B9Facts
• SYNONYMS:
– Vit B9, Folate, Folacin, PGA (Pteroylglutamic acid)• FUNCTION
– One-Carbon metabolism– Essential in biosynthesis of thymidine, AA, and
purine
FOLIC ACID B9Facts
• FOOD SOURCES– Green leafy vegetables, liver, lima beans, whole
grain cereals• DEFICIENCY
– Growth failure – Megaloblastic anemia– Neural tube defects
FOLIC ACID B9Structure
FOLIC ACID B9Structure
For transfer and utilization of the single carbon moiety.
FOLIC ACID B9Functions
– Carrier of one-carbon group moieties.
Form Formula Name
Most reduced CH3 Methyl
Intermediate CH2 Methylene
Most oxidized CHO Formyl
CHNH Formimino
CH= methenyl
FOLIC ACID B9Forms
Form Decription
N5-methyl- THFA Most prevalent form transported in the blood
N5, N10-methylene THFA Provides methyl group in the formation of thymidylate for DNA synthesis and erythrocyte formation
N10 formy; THFA Provides C atom that becomes C2 of purinenucleus
N5-formimino THFA Histidine catabolism
N10-hydroyxymethyl THFA Thymine synthesis
FOLIC ACID B9Function
FOLIC ACID B9Function
400 ug folate supplement
FOLIC ACID B9Deficiency
Blood Cell Macrocytic Anemia- impaired production
Blood Cell Microcytic Anemia
Results when RBC are unable
to divide…
THFA
THFATHFA
VITAMIN B12Definition
• SYNONYMS:
– Antipernicious anemia vitamin
– Cobalamin
– Extrinsic Factor of Castle
– Erythrocyte Maturation Factor
• CHEMISTRY:
VITAMIN B12Chemistry
• Consists of:
1. Corrin ring system - central portion of the molecule: similar to a porphyrin ring
2. 5,6-dimethylbenzimidazole riboside
3. Aminopropanolol
4. Propionic acid
5. Cobalt-occupies the center of the corrin ring system
1
5
43
2
VITAMIN B12Function
• FUNCTION– Synthesis of methionine
– Isomerization of methylmalonyl CoA
VITAMIN B12Function
– Involved in the rearrangement of methylmalonyl CoA to succinyl CoA by methylmalonyl CoA isomerase
• Involved in the transfer of a methyl group from methylTHFA to homocysteine to form methionine .
B-12
B-12B-12
VITAMIN B12Sources І Deficiency
• FOOD SOURCES– Synthesized by microorganisms in the bacterial flora
– Liver, whole milk, eggs
– oysters, fresh shrimp, pork, chicken
• RDA– Children: 2ug/day
– Adults 3 ug/day
– Pregnancy and lactation: 4 ug/day
• DEFICIENCY– Abnormal fatty acid synthesis
– Cell membrane defects/Neurological abnormalities
– Pernicious anemia
VITAMIN B12Forms
Forms Content
Cobalamin Without cyanide
Cyanocobalamin with cyanide group
Hydroxocobalamin with hydroxyl group, more active in enzyme systems; retained longer in the body
Methylcobalamin major form in the plasma
5’-deoxyadenosylcobalamin
readily binds to plasma-binding proteins
VITAMIN B12Deficiency
• Causes:
– Chronic dietary deficiency of vitamin B-12.
– Poor absorption due to lack of intrinsic factor.• Presence of antibodies to the intrinsic factor in the gastric
juice.
• Lack of secretion of intrinsic factor (due to gastric mucosal cell atrophy or due to total gastrectomy.
• Extensive resection of the small intestines.
– Increased requirements as in pregnancy.
VITAMIN B12Deficiency
• Clinical effects: “Pernicious Anemia”
• No healthy RBC
• Characterized by:
– Megaloblastic or macrocytic anemia.
– Lesions of the nervous system
– Mucosal atrophy and inflammation of the tongue (glossitis), mouth (stomatitis) and pharynx (pharyngitis)
ASCORBIC ACID Facts
• Anti-scorbutic vitamin
• Very sensitive to oxidation
• Rapidly destroyed by alkalies
• Freezing has no deleterious effect
• Strong reducing agent
• Drying vegetables usually results in loss of vitamin C.
• Pasteurizing milk destroys vitamin C
ASCORBIC ACID Facts
• Sources:
– Citrus fruits
– Tomatoes
– Strawberries
– Green vegetables
– Guava fruit
– Green pepper
• RDA:
– Adults: 60 mg/day
– Children: 40 mg/day
SYNTHESIS AND CATABOLISM OF ASCORBIC ACID
ASCORBIC ACID Facts
ASCORBIC ACID Metabolic roles
Hydroxylation of Proline and
Lysine in collagen formation.
Hydroxylation of tryptophan Synthesis of
norephinephrine
Tyrosine metabolism
Hydroxylation of steroids in the adrenal cortex
Serves as a reductant of
ferric to ferrous ion
Involved in the conversion of folic acid to active THFA
Involved in the hydroxylation of cholesterol to
cholic acid
Acts as regulator of cholesterolmetabolism
ASCORBIC ACID Function
• Major function of vitamin C– coenzyme in the formation of tissue collagen or intracellular cement
substance
ASCORBIC ACID Function
• Major function of vitamin C– coenzyme in the formation of tissue collagen or intracellular cement
substance
ASCORBIC ACID Deficiency
• Spongy gums
• Poor wound healing
ASCORBIC ACID Deficiency
• Splinter hemorrhages in nails
• Petechial, subcutaneous hemorrhages
ASCORBIC ACID Deficiency
• Scorbutic rosary beads -swelling at the ends of long bones
FAT-SOLUBLE VITAMINSStructure
• Vitamin A retinol, B-carotenes
• Vitamin D cholecalciferol
• Vitamin K phylloquinones, menaquinones
• Vitamin E tocopherols
VITAMIN A RetinolStructure
Β-carotene dioxygenase + bile Acids
Retinaldehyde reductase + NADH, NADPH
VITAMIN A RetinolStructure
• Retinol and retinoic acid – act like steroid hormones
• Retinalehyde is a component of Rhodposin
• Retinoic acid participates in glycoprotein synthesis
VITAMIN A RetinolFunction
• Provitamin - β carotene
• FUNCTION– Maintenance of reproduction
– Maintenance of vision
– Promotion of growth
– Gene expression
– Treatment of psoriasis, acne, cancers
• FOOD SOURCES– Liver, kidney, cream, butter, egg yolk
– Yellow and dark green vegetables
VITAMIN A RetinolFunction
RAR and RXR form RAR/RXR heterodimers, which bind to regulatory regions of the chromosome called retinoic acid response elements (RARE). Binding of all-trans-RA and 9-cis-RA to RAR and RXR respectively allows the complex to regulate the rate of gene transcription.
ACTION OF RETINOIDS
VITAMIN D Facts
• FUNCTION
– 1,25-dihydrocholecalciferol- a steroid hormone
– Stimulates gene expression or repress gene transcription
– Regulates plasma levels of calcium and phosphorus
• FOOD SOURCES
– Liver, kidney, fatty fish, egg yolk
VITAMIN D Action
Response to low
plasma calcium
VITAMIN D Action
Response to low
plasma calcium
VITAMIN D Deficiency
• DEFICIENCY– Rickets
– Osteomalacia(demineralization of bone)
• TOXICITY– Most toxic of all vitamins
– Deposition of calcium in organs and arteries, kidney stones
VITAMIN K Function
• FUNCTION
– Post-translational modification of various blood clotting factors
– Phylloquinone (plants)
– Menaquinone (intestinal bacterial flora)
– Menadione
• FOOD SOURCES
– Cabbage, cauliflower, spinach, egg yolk, liver
VITAMIN K Function
VITAMIN K Function
VITAMIN K Warfarin is a vitamin K antagonist that inhibits the recycling of vitamin K at two dithiol-dependent steps.
VITAMIN E Function
• FUNCTION– -tocopherol
– Anti-oxidant
• FOOD SOURCES– Vegetable oils, liver, eggs
• DEFICIENCY– Heart disease
– Defective cell membranes
– Cataract formation
• TOXICITY– No toxicity at 300 mg/day
VITAMINSDefinition I Function
VITAMIN FUNCTIONS DEFICIENCY DISEASE
A Retinol, β-carotene
Visual pigments in the retina; regulation of gene expression and cell differentiation;Antioxidant
Night blindness, xerophthalmia;keratinization of skin
D Calciferol Maintenance of calcium balance; enhances intestinal absorption of Ca++ and mobilized biomineral
Rickets = poor mineralization of bones;Osteomalacia = bone demineralization
E TocopherolsTocotrienols
Antioxidant, especially in cell membranes
Extremely rare - serious neurologic dysfunction
K PhylloquinoneMenaquinone
Coenzyme in formation of γ-carboxyglutamate in enzymes of blood clotting and bone matrix
Impaired blood clotting, hemorrhagic disease
VITAMINSDefinition I Function
VITAMIN FUNCTIONS DEFICIENCY DISEASE
B1 Thiamin Coenzyme in pyruvate and α-ketoglutarate DH, and transketolase; poorly defined function in nerve conduction
Peripheral nerve damage (beriberi) or CNS lesions (Wernicke-Korsakoffsyndrome)
B2 Riboflavin Coenzyme in redox reactions; prosthetic group of flavoproteins
Lesions of corner of mouth, lips and tongue,seborrheic dermatitis
B3 Niacin Nicotinic acidNicotinamide
Coenzyme in redox reactions; functional part of NAD and NADP
Pellagra- photosensitivedermatitis, depressive psychosis
Energy-Releasing
VITAMINSDefinition I Function
Energy-Releasing
VITAMIN FUNCTIONS DEFICIENCY DISEASE
Pantothenic Acid Functional part of CoA and acylcarrier protein: fatty acid synthesis and metabolism
H Biotin Coenzyme in carboxylationreactions in gluconeogenesisand fatty acid synthesis
Impaired fat and CHO metabolism, dermatitis
VITAMINSDefinition I Function
VITAMIN FUNCTIONS DEFICIENCY DISEASE
Folic acid Coenzyme in transfer of one-carbon fragments
Megaloblastic anemia
B12 Cobalamin Coenzyme in transfer of one-carbon fragments and metabolism of folic acid
Pernicious anemia = megaloblastic anemiawith degeneration of the spinal cord
Hematopoeitic
VITAMINSDefinition I Function
VITAMIN FUNCTIONS DEFICIENCY DISEASE
B6 PyridoxinePyridoxalPyridoxamine
Coenzyme in transamination & decarboxylation of AA and glycogen phosphorylase; role in steroid hormone action
Disorders of AA metabolism, convulsions
C Ascorbic Acid Coenzyme in hydroxylation of proline and lysine in collagen synthesis; antioxidant; enhances iron absorption
Scurvy- impaired wound healing, loss of dental cement, subcutaneous hemorrhage
Other functions
VITAMINSDefinition I Function
• w
