1. Co-enzymes and cofactors activity in enzymes

2. Many Enzymes Require Cofactors for Activity
A cofactor is a small non-protein molecules that is bound (either tightly or loosely) to an enzyme and is required for catalysis.
Catalytic activity of many enzymes depends on the presence of cofactors. 2

3. Many Enzymes Require Cofactors for Activity

4. Types of cofactors 4 4

5. Essential Ion Cofactors
Activator ions – bind reversibly to enzyme and often participate in substrate binding.
Metal ions of metalloenzymes – cations that are tightly bound to enzyme and participate directly in catalysis (Fe, Zn, Cu, Co).
Metal activated enzymes – require or are stimulated by addition of metal ions (i.e. Mg2+, is required by many ATP requiring enzymes)

6. inorganic cofactors Functions of iron
Iron must be present in hemoglobin in order to pick oxygen
Electron transport
Oxygen binding
Oxygen carrier

7. Function Oxygen Transport & Storage
Hemoglobin
Myoglobin
Electron Transport & Energy Metabolism
Cytochromes
Fe-S proteins
Substrate Oxidation & Reduction
– Iron dependent enzyme-
Ribonucleotide reductase
Amino acid oxidases
Fatty acid desaturases
Nitric oxide synthetase
Peroxidases
HEME is synthesized in the liver from succinyl-CoA and Glycine.
Hemoglobin represents more than 95% of the proteins of the red blood cell, and contains about 60% of the body iron.
Function1) transport O2from the respiratory organ to peripheral tissue
2)Transport of CO2 and proteins from peripheral tissues t the lung for subsequent excretion
3)transport NO. 2,3-bisphosphoglycerate, an intermediate in glycolysis, stabilizes the tettrameric structure of hemoglobin, indicateing another important function of glycolysis in the functions of red blood cells. (Iron dificient, heme decreases leading O2 transport and NO transport decrease--- Vascular systeem decreases and immune system decrease)
Myoglobin is a single polypeptide chain (MW16900). Contains about4% of the body’s iron. Myoglobin is the minor protein of muscle cells and is used for the short term storage of oxygen.
Electron transport: In cytochromes, the oxidation and reduction of the iron atom are essential to their biological function. By contrast, oxidation of the Fe2+ to Fe3+ of hemoglobin or myoglobin destroys biological activity.
All use O2 as a substrate

8. Examples of Iron-dependent Enzymes
Aldehyde Oxidase
R-CHO + O2  RCOOH + H-O-O-H
Tryptophan 5-monooxygenase
L-tyrptophan + BH4 + O2  5 OH L-tryptophan + BH2 + H2O
Fatty Acid desaturase
Stearoyl-CoA + NADH + H+ + O2  Oleoyl-CoA + NAD H2O
Peroxidase
2H2O2  2H2O + O2
(O2 is either incorporated into the product or reduced by electrons)

9. Inorganic cofactors
Mg2 is used in glycolysis. In the first step of converting glucose to glucose 6-phosphate
before ATP is used to give ADP and one phosphate group, ATP is bonded to Mg2 which stabilizing the other two phosphate groups so it is easier to release only one phosphate group without resonate with other two.

10. Zinc Function 300 enzymes require zinc numerous hormones require zinc
DNA, RNA polymerases
numerous hormones require zinc
insulin
transcription factors (zinc finger proteins)
membrane stability
myelination
skeletal development

11. Example of prosthetic group
Example of metalloenzyme: carbonic anhydrase contains zinc
Metalloenzymes contain firmly bound metal ions at the enzyme active sites (examples: iron, zinc, copper, cobalt).
One of the functions of the enzyme interconvert carbon dioxide and bicarbonate to maintain acid-base balance in blood and other tissues, and to help transport carbon dioxide out of tissues. A zinc prosthetic group in the enzyme is coordinated in three positions by histidineside-chains. The fourth coordination position is occupied by water This causes polarisation of the hydrogen-oxygen bond, making the oxygen slightly more negative, thereby weakening the bond.

13. Examples of enzymes containing this ion
Cupric
Cytochrome oxidase
Ferrous or Ferric
Cytochrome (via Heme) Hydrogenase
Magnesium
Glucose 6-phosphatase Hexokinase
Manganese
Arginase
Molybdenum
Nitrate reductase Nitrogenase
Nickel
Urease
Zinc
Alcohol dehydrogenase Carbonic anhydrase

14. Coenzyme Coenzymes are small organic non-protein molecules.
Loosely attached to apoenzymes, seperated easily by dialysis they are often called cosubstrate or secondary substrate.
Reaction involving:
oxidoreduction,
group. transfer,
Isomerization and
covalent bond formation req. coenzyme.

15. Coenzymes + apoenzyme coenzyme holoenzyme Non-Protein Total Protein
Organic molecule that temporarily binds to apoenzyme in order for it to work +
apoenzyme coenzyme holoenzyme
Non-Protein
Total
Protein

16. The functional role of Coenzymes is to act as transporters of chemical group
A coenzyme is a necessary helper for enzymes that assist in biochemical transformations.
These molecules act to transfer chemical groups between enzymes or from Enzyme to substrate or product.
A coenzyme Transport a variety of chemical groups (Such as Hydride, Acetyl, Formyl, Methenyl or methyl).

17. Vitamin Insufficiency Generally Result in malfunction of enzymes
Main clinical symptoms of dietary vitamin insufficiency generally arise due the malfunction of enzymes.
Dietary vitamin insufficiency leads to a lack of sufficient cofactors derived from vitamins to maintain homeostasis.

18. Vitamins of B complex group acting as co-enzymes
active form (co-enzyme)
Thiamine Vitamin B 1
TPP (thiamine pyrophosphate)
Riboflavin Vitamin B 2
FMN, FAD
Niacin Vitamin B 3
NAD,NADH
Pantothenic acid Vitamin B 5
component of coenzyme A
Pyridoxine Vitamin B 6
PLP (pyridoxal phosphate)
Biotin
Folic acid
THF (Tetrahydrofolate)
Cobalamine Vitamin B 12
cobamide

19. Vitamin B1 - Thiamine Entity Transferred; Aldehydes
The active form is thiamin pyrophosphate (TPP)
Thiamin is rapidly converted to thiamin pyrophosphate (TPP) in small intestine, brain and liver.
TPP is formed from thiamin by the action of thiamine diphosphotransferase.
TPP coenzyme is required by enzymes in the decarboxylation of -keto acids.
Entity Transferred; Aldehydes
TPP coenzyme is required by enzymes in the decarboxylation of -keto carboxylic acids.

20. TPP as co-enzymes
(TPP) is a derivative of  thiamine (vitamin B1). Nutritional deficiency of thiamine leads to the disease beriberi. Beriberi affects especially the brain, because TPP is required for carbohydrate metabolism, and the brain depends on glucose metabolism for energy

21. Riboflavin functions, vit B2
Active forms are
Flavin adenine dinucleotide (FAD)
Flavin mononucleotide (FMN)
These play key roles in hydrogen transfer reactions associated with
Glycolysis
TCA cycle
Oxidative phosphorylation. 21

22. Regulated by ACTH, aldosterone, and thyroid hormone
p. 283b

23. In tissues, riboflavin is typically converted to its coenzyme forms by flavokinase and FAD synthetase. Synthesis is under hormonal control. ACTH, aldosterone, and thyroid hormones all accelerate conversion of riboflavin to its coenzyme forms.
p. 283c 23

24. FAD As co-enzyme

25. Vitamins and Derivatives Involved in Group Transfer Reactions
Nicotine Adenine Dinucleotide (NAD) & Nicotine Adenine Dinucleotide Phosphate (NADP)
Derivative of Niacin (B3)
Serve as cofactors in oxidation / reduction reactions
Act as co-substrates for dehydrogenases
Entity Transferred; Hydride ion (H+ + 2e-) Electron (Hydrogen atom)

26. H+ (a reaction of glycolysis) glyceraldehyde 3P + NAD
(substrate) (co substrate)
dehydrogenase
(enzyme )
DiPhosphoglyceric acid + NADH
(product) (NAD act as
co-enzyme & H
acceptor) H+

27. Entity Transferred; Acetyl group and other acyl groups
Coenzyme A (CoA)
Derivative of Pantothenic acid (B5)
Entity Transferred; Acetyl group and other acyl groups
needed for energy production as well as glucose and cholesterol synthesis Deficiency can result in fatigue, retarded growth, cramps, and anemia

28. Pyridoxal Phosphate PLP is Derivative of Pyridoxine (Vit. B6)
involved in :
Transamination reactions required for the synthesis and catabolism of the amino acids.
Decarboxylation reactions.
Entity Transferred; Amino Groups(-NH2)

29. Example of co-enzyme in amino acid metabolism
NH2
Glutamate + pyruvate + pyrodoxal P
(co-substrate,acceptor
Transaminase & donor of amino group)
(enzyme)
α-Ketoglutaric acid + Alanin

30. is a coenzyme for enzymes that transfer carboxyl groups
Biotin
is a coenzyme for enzymes that transfer carboxyl groups
Entity Transferred; Carbon Dioxide
is a coenzyme for enzymes that transfer carboxyl groups