lecture 14 Flashcards
vitamins and cofactors
identify the essential vitamins
fat-soluble and water soluble (B-complex and Vitamin C)
what does “Vita” mean? what do they do for the body?
life, all vitamins are essential
Organic compounds distinct from fats, carbohydrates or protein.
Natural components of foods, usually present in minute amounts.
Not synthesized by the body in amounts to meet our physiologic needs.
Essential for normal physiologic function (maintenance, growth, etc.)
Cause a specific deficiency syndrome by their absence or insufficiency.
what are the water soluble vitamins?
so previously mentioned, the water-soluble vitamins can be divided up into B-complex and vitamin C; the B complex vitamins include:
Thiamin (B1) Riboflavin (B2) Niacin (B3, nicotinic acid, nicotinamide) Pantothenic acid (B5) Biotin (B7) Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine) Folate (B9) Vitamin B12 (cobalamin)
other name for Thiamin?
B1
other name for Riboflavin?
B2
other name for Niacin?
B3 or nicotinic acid, nicotinamide
other name for Pantothenic acid?
B5
other name for Biotin?
B7
other name for vitamin B6?
pyridoxine, pyridoxal, pyridoxamine
other name for folate?
B9
other name for Vitamin B12?
cobalamin
name the fat-soluble vitamins?
Vitamin A,D,E,K
water soluble vitamins are readily stored, T/F?
T, they are readily stored except for vitamin B12
water soluble vitamins are toxic, T/F?
F, no known toxicity
where are the fat soluble vitamins stored?
adipose tissue and serves as a potential for toxicity
whats the clinical significance for fat soluble vitamins?
fat absoption disorders, which mean fat soluble malnutrition
what are some examples of fat absorption disorders of fat soluble vitamin malnutrition?
inflammatory bowel syndrome, gastrectomy, pancreatic insufficiency, liver disease
what is a cofactor?
small, non-protein, organic molecule or metal ion that work in concert with an enzyme to catalyze biochemical reactions; they provide chemical reactivity or structural properties and these drive special reactions
what is the catalysis of cofactors like?
its limited to specific AA side chains and these side chains can do all the chemistry that is required
what is the purpose of the cofactor?
Purpose of cofactors bind to active site and chemistry occurs here and helps to facilitate the reaction and if the enzyme using a cofactor must have it everytime and so if it isn’t present then the reaction will not happen
what are the two examples of cofactors used in this lecture?
essential ions and coenzymes
*Name the essential ions? Name the coenzymes?
activator ions and metal ions of metalloenzymes; cosubstrates and prosthetic group
*describing the binding of the activator ions and the metalloenzymes? both of these are what types of ions?
loosely bound; tightly bound; both fall under essential ions
*describe the binding of cosubstrates and prosthetic groups; both of these are what types of ions?
loosely bound; tightly bound; both fall under coenzymes
*what does loosely bound mean? examples?
molecule/ion will bind to the enzyme, carry out the reaction, dissociate from the enzyme; ATP and Mg2+
*what does tightly bound mean? examples?
these may be covalently attached to the enzyme residue at the active site and can also bind non-covalently with very high affinity; **hemes are generally covalently bound as is biotin and lipoic acid. **Flavins on the other hand bind non-covalently but very slightly; ***Zn2+ ions by electrostatic bonds
what are metabolite cofactors? examples?
molecules that are produced by metabolic pathways and used by other enzymes to carry out key reactions; ATP and SAM note that the gamma end of the ATP is the donor and a methyl group from SAM (refer to picture); GTP, UTP, CTP, ATP all used in DNA synthesis
what are the vitamin derived cofactors?
thiamine pyrophosphate - Vitamin B1 /thiamin
FAD and FMN - Vitamin B2/riboflavin
NAD+/NADP - Vitamin B3/niacin
Pantothenic Acid - Vitamin B5/pantothenate
pyridoxal phosphate - Vitamin B6/Pyridoxine
Biotin - Vitamin B7
tetrahydrofolate - Vitamin B9/folate
adenosylcobalamin/methylcobalamin - cobalamin (B12)
Vitamin C - ascorbic acid or itself
Vitamin K - itself
high levels of homocysteine is not good for the heart and so it is regulated by what metabolite cofactor?
S-adenosylmethionine
vitamin derived cofactors can be synthesized by the body, T/F?
False
what is Vitamin B1 used for? its cofactor?
energy transformations and carboxylations, its cofactor is thiamine pyrophosphate (TPP); also seen in transketolase reactions required for synthesis of NADPH and Pentoses
what is the importance of vitamin B2? its cofactor?
the cofactors are FAD and FMN; FAD, FMN is the oxidized form and the reduced form is the FMNH2, FADH2. We see this in fatty acid metabolism, the ETC, glycolysis. Its overall purpose is for electron transport to mitochondria to drive ATP production
what is the importance of vitamin B3? its cofactor?
note that Vitamin B3 or Niacin can have two forms, its oxidized form NAD+ or NADH its reduced form- both serving as the cofactor for this vitamin. The cofactors are used in redox reactions involving the Hydride ion, aka electron transfer
what is the cofactor NAD used in?
glycolysis, oxidation reactions like oxidative decarboxylation of pyruvate to acetyl CoA, oxidation of acetyl CoA in the TCA Cycle, Beta oxidation of fatty acids and oxidation of ethanol
what is the cofactor NADP used in?
biosynthesis of molecules like fatty acids, cholesterol and steroid hormone synthesis, deoxy ribonucleotide synthesis, glutathione, Vitamin C, thioredoxin regeneration, folate coenzyme synthesis
lactate is more reduced or oxidized?
reduced
pyruvate is more reduced or oxidized?
oxidized
lipoamide is a B vitamin, T/F?
F, it is not
what is lipoamide formed from?
lipoic acid
lipoamide is covalently bound to a Lys residue side chain of the enzyme, T/F?
True
name two characteristics of Lipoamide?
1) Prosthetic group
2) works with other B vitamin cofactors
what is significant about the geometry of the lipoamide molecule?
it can move around and interact with different parts of substrates and find a hydrophobic or charged area and can sometimes participate in two different chemical reactions (it is thought to swing form one active site to another in multi-enzyme complex carrying acyl group)
lipoamide can be an Acyl carrier and also has redox properties, T/F?
True, note that the Acyl group has a carboxylic acid group
what are the redox properties of Lipoamide?
ring form with S-S bond is oxidized form and ring form with -SH group is reduced form, also remember that NADH is produced form NAD+ when lipoamide is oxidized
what are the functions of Lipoamide?
acyl group carrier and also has redox properties
what is the cofactor of Vitamin B5?
Coenzyme A, it participates as an acyl carrier group
what is the purpose of pantothenic acid?
used to form a part of Coenzyme A which is essential for energy production form macronutrients, used as an acyl carrier group, acyl group attaches to sulfur.
what is the business end of coenzyme A?
the sulfur attached to B-mercaptoethylamine is the site of attachment and sulfurs like to form thioester bonds, moreso acyl groups and so it is an acyl carrier group and carries things like the acetate group
T/F, CoA binds to fatty acid really well because of the polar nature of the CoA?
T, CoA has the power to bind a fatty acid, which is hydrophobic, and act as carrier group to transport it into the cytoplasm. Solubility of the molecule can overcome the insoluble end of the fatty acid and no it can travel around in the aqueous environment and worked on
what is Vitamin B6 also known as?function?
pyridoxine; amino acid metabolism, note that on the cofactor, the aldehyde is the business end and hydrogen can be pulled off to allow for other binding.
what is the cofactor of Vitamin B6?
pyridoxal phosphate (PLP; coenzyme form)
what reactions can the cofactor of Vitamin B6 participate in? what is the cofactor again?
transamination (Oxaloacetate participates in this reaction and important in the TCA cycle, completely reversible reaction), isomerization, decarboxylation, side chain removal; pyridoxal phosphate
what is the other name for Vitamin B7?
Biotin
what is the cofactor for Vitamin B7? how does it bind?
used as is; covalently attached to enzyme lysine chain
what is biotin used for?
since biotin is used as is, we see it used in carboxylation reactions (CO2 transfer) in metabolism:
transforms pyruvate to oxaloacetate
transforms acetyl CoA to Malonyl CoA which this one is used in fatty acid synthesis
What is Vitamin B9 also known as?
folate
what is the cofactor for Vitamin B9?
tetrahydrofolate
what is the function of tetrahydrofolate?
it transfers single carbon units (methyl, methylene, and methenyl, even aldehyde) and the two nitrogen atoms are the sites of function
how binds do each of the carbons need above?
methyl group needs 1, methylene group needs 2, methenyl group needs 3
what is tetrahydrofolate critical for?
neurological function, neurological development in the fetus, synthesis of methionine and synthesis of nucleic acids
what is the other name for Vitamin B12?
cobalamin
what are the cofactors of Vitamin B12?
Adenosylcobalamin, Methylcobalamin, Cyanocobalamin
what are the cofactors of vitamin B12 used for?
Adenosylcobalamin: catalyzes exchange reactions (isomerizations)
Methylcobalamin: transfers methyl groups
Cyanocobalamin: common dietary form
why is the methylcobalamin cofactor important as the cofactor for VB12?
its integral in methionine synthesis which is important in the production of red blood cells. Homocysteine is an intermediate in methionine synthesis and so this is where Tetrahydrofolate donates a methyl group and we see how this cofactor drives the reaction
what is the other name for Vitamin C?
ascorbic acid
what synthesizes ascorbic acid?
plants and animals, and in animals its synthesized from glucose and galactose
what are the functions of vitamin C?
oxidation-reduction reactions which means it easily loses electrons and is used in the collagen formation which keeps iron in ferrous form enabling hydroxylation enzymes to function; its also an antioxidant that eliminates free radicals
whats vitamin A important for?
vision which is essential to photoreception important in the production of 11-cis-retinal isomerize to trans retinal and allows for nerve signaling so we can see
where is vitamin D synthesized from?
sunshine vitamin and synthesized from UVB light and cholesterol
what are the functions of Vitamin D?
hormone, most commonly a steroid hormone
what are the precursors for Vitamin D?
for animals its 7-dehydrocholesterol transformed into cholecalciferol (D3) and for plants its Ergosterol transformed into ergocalciferol (D2)
what is the storage form of Vitamin D?
25-Hydroxycholecalciferol
what is the active form of Vitamin D?
1,25-Dihydroxycholecalciferol
what is the function of Vitamin D?
steroid hormone used in gene transcription and is used in the maintenance of calcium and phosphorus homeostasis; mostly know for calcium homeostasis
what are the two classes of biologically active substances for Vitamin E?
tocopherols (protects mitochondrial membrane) and tocotrienols, where tocopherols are the most biologically active
what is the function of Vitamin E?
a membrane antioxidant that protects lipids from oxidation by ROS, very lipid soluble and kills ROS by adding a Hydrogen
what are the two forms of Vitamin K?
Phylloquinones (synthesized by green plants) and Menaquinones (synthesized by bacteria_
what is the function of Vitamin K?
its the clotting vitamin and is implicated in blood coagulation, i.e. - coumadin/warfarin
what vitamins have cofactors (THF and Methycobalamin) that work together in methionine synthesis?
Vitamin B9 and B12
what is a cosubstrate?
loosely bound coenzymes
what is prosthetic group?
tightly bound coenzymes
what is activator ions?
loosely bound essential ions
what are metal ions?
tightly bound essential ions
what are the metabolite cofactors?
molecules produced in metabolic pathways, ATP, SAM, GTP, UTP, CTP, ATP used in DNA synthesis
