Cofactors, Coenzymes, Abzymes and Ribozymes.pptx

1. CO-FACTORS, CO-ENZYMES,
RIBOZYMES AND ABZYMES
BIOCHEMISTRY
Submitted to:
Dr. Elsam Joseph
Assistant professor
Department Of Botany
Submitted by:
Ananya J.S.
Roll No: 5
1ST MSc Botany

2. • Enzyme’s catalytic activity depends upon the integrity of it’s
protein structure

3. CO-FACTORS
• Co-factors are non-protein molecules that assist enzymes during
the catalysis of reactions
• Such an enzyme without it’s co-factor is referred as apoenzyme.
• The complete catalytically active enzyme known as holoenzyme.

5. • Co-factors can be subdivided into metals and small organic molecules
• Co-factors that are small organic molecules is co-enzymes.
• Most common co-factor are metal ions.
• If tightly bound, the co-factors are called prosthetic groups.
• Loosely bound co-factors serve functions like those of prosthetic groups
but bind in a transient manner either to the enzyme or to substrate.
• They are more like co substrates because they bind and release from
enzyme just as they do.
Co-factor Types

8. Prosthetic Groups
• Tightly integrated into the enzyme structure by covalent or non-
covalent bond.
(a) Organic
• Pyridoxal phosphate
• Flavin mononucleotide (FMN)
• Flavin adenine dinucleotide (FAD)
• Thiamin pyrophosphate (TPP)
• Biotin

9. (b) Inorganic
Metals are the most common prosthetic groups.
Metal ions; Co, Cu, Mg, Mn, Zn, Fe

10. • Enzymes that contain tightly bound metals are termed
metalloenzymes.
• Enzymes that require metal ions as loosely bound co-factors
are termed as metal- activated enzymes.
• Metal ions facilitate;
1. Binding and orientation of substrate
2. Formation of covalent bonds with reaction intermediates
3. Interact with substrate to render them more electrophilic or
nucleophilic

11. Examples Of Metalloenzymes

12. • In a few enzyme-controlled reactions, it is the presence of certain
ions that can increase the reaction rate.
• Ions may combine with the enzyme or the substrate.
• The ion binding makes the formation of an enzyme-substrate
complex happen more easily, because it can affect the charge
distribution or the end shape of the complex.
Metal Activated Enzymes

13. • Amylase catalyzes the breakdown of maltose molecules.
• This enzyme will function properly only if chloride ions are present.
• Without the chloride ions, amylase cannot catalyze the reaction.
Starch + Cl- + α amylase → Maltose+ intermediate formation of dextrins

14. CO-ENZYMES
• Coenzyme is a substance that enhances the action of an enzyme.
• The catalytic activity of enzymes mostly depends on the presence
of non-protein compounds called coenzymes.
• Coenzymes cannot be isolated from apoenzymes without
denaturation of the enzyme proteins.

15. • Coenzymes are small molecules.
• They cannot by themselves catalyze a reaction but they can help
enzymes to do so.
• In technical terms, coenzymes are organic nonprotein molecules
that bind with the protein molecule (apoenzyme) to form the
active enzyme (holoenzyme).
• A number of the water-soluble vitamins such as vitamins B1, B2
and B6 serve as coenzymes.

16. • Coenzyme (Biology definition): Molecule required by a particular
enzyme to carry out catalysis of a chemical reaction is called as
coenzyme.
• Examples of coenzymes:
> Nicotineamideadinine dinucleotide (NAD),
> Nicotinamide adenine dinucelotide phosphate (NADP), and
> Flavin adenine dinucleotide (FAD).
These three coenzymes are involved in oxidation or hydrogen transfer.

17. Example for co-enzyme
• Succinate dehydrogenase catalysed reaction
• FAD act as co-enzyme.

19. I. Cosubstrate (loosely bound): A coenzyme substrate is loosely bound to
an enzyme and dissociates in an altered form as part of the catalytic cycle.
Examples:
ATP
S-Adenosyl Methionine
Uridine Di Phosphate-sugar
NAD+/NADP+
Coenzyme Types
Tetrahydrofolate
COA
Ubiquinone protein coenzymes

20. Cosubstrate coenzyme

21. II. Prosthetic group(tightly bound): A coenzyme prosthetic group is tightly
bound to the enzyme and remains bound during the catalytic cycle.
• A coenzyme that is tightly or even covalently, and permanently bound
to a protein.
• Both prosthetic groups and cosubstrates have the same function, which
is to facilitate the reaction of enzymes and proteins.
Example:
FMN/FAD
Thiamine Pyro Phosphate
Pyridoxal Phosphate
Biotin
Adenosyl/methylcobalamin
Lipoic acid/ lipoamide

22. Prosthetic group coenzyme (TPP)

23. • Coenzyme can be classified according to the group transferred. Based
on the above concept, we may classify coenzymes as follows:
1. For transfer of groups other than hydrogen groups
CO-A
TPP
2. For transfer of hydrogen
NAD, NADP
FAMN, FAD
PLP
Biotin
Lipoic acid
Coenzyme Q

24. Coenzyme – transfer of groups other than hydrogen groups
(Transfer of acyl group)

25. Coenzyme – transfer of hydrogen group

26. Coenzyme – Functions
• The coenzyme is essential for the biological activity of the enzyme.
• A coenzyme is a low molecular weight organic substance, without
which the enzyme cannot exhibit any reaction.
• A coenzymes prepares the active site for catalytic activity.
• The function of coenzyme is to transfer of groups between enzymes.
• A coenzyme is necessary helper for enzymes that assist in biochemical
transformations.
• A coenzyme transport a variety of chemical groups (such as Hydride,
Acetyl, Formyl, Methenyl, Methyl)

27. RIBOZYME
S
• A ribozyme is an RNA molecule with a well defined tertiary structure.
• Ribozyme means ribonucleic acid enzyme. It may also be called an RNA
enzyme or catalytic RNA.
• It contains an active site that consists entirely of RNA.
• A ribozyme can catalyzes a chemical reaction. Many natural ribozymes
catalyze either the hydrolysis of one of their own phosphodiester
bonds(self-cleaving ribozymes), or the hydrolysis of bonds in other RNAs.

28. • They have been found to catalyze the aminotransferase activity of the
ribosome.
• Examples of ribozymes include the hammerhead ribozyme, the VS
ribozyme and the hairpin ribozyme.

29. Ribozyme cleavage of RNA

30. Hummerhead Ribozyme

31. Secondary structures of in cis and in trans
hammerhead ribozymes.

32. Ribozyme Action

33. Ribozyme Activity
• Although most ribozymes are quite rare in the cell, their roles are
sometimes essential to life.
• For example, the functional part of the ribosome, the molecular
machine that translates RNA into proteins, is fundamentally a ribozyme,
composed of RNA tertiary structural motifs that are often coordinated
to metal ions such as Mg2+ as cofactors.
• RNA can also act as a hereditary molecule, Walter Gilbert propose that,
the cell used RNA as both the genetic material and the structural and
catalytic molecule. This hypothesis is known as the “RNA world
hypothesis” of the origin of life.
• Involve in packing of viral genetic material into virions.

34. Naturally Occurring Ribozymes
• Peptidyl transferase 23S rRNA
• Rnase P
• Group I and Group II introns
• GIR1 branching ribozyme
• Leadzyme
• Hairpin ribozyme
• Hammerhead ribozyme
• HDV ribozyme
• Mammalian CPEB3 ribozyme
• VS ribozyme
• glmS ribozyme
• CoTC ribozyme

35. Artificial Ribozymes
• Synthetic ribozymes made in the laboratory
• Some have novel structures, while some were similar to the naturally
occurring hammerhead ribozyme.
• The techniques used to discover artificial ribozymes involve Darwinian
evolution. This approach takes advantage of RNA’s dual nature as both a
catalyst and an informational polymer, making it easy for an investigator
to produce vast populations of RNA catalysts using polymerase enzymes.
• The ribozymes are mutated by reverse transcribing them with reverse
transcriptase into various cDNA and amplified with mutagenic PCR.

36. Applications
• A type of synthetic ribozyme directed against HIV RNA called gene
shears has been developed and has entered clinical testing for HIV
infection.
• Ribozymes for human therapy: The ability of ribozymes to recognize
and cut specific RNA molecules makes them exciting candidates for
human therapy.

37. ABZYMES
• Abzymes are catalytic antibodies having structural complementarity for
the transition state of an enzyme catalyzed reaction.
• An abzyme (from antibody and enzyme), also called catmab (from
catalytic monoclonal antibody), and most often called catalytic
antibody, is a monoclonal antibody with catalytic activity.
• They bind strongly to the transition state with high association
constant, enhancing the reaction rate.
• Abzymes reduce rotational entropy.

38. Sources Of Abzymes
• Abzymes are usually artificial constructs.
• They also obtained from human and
animal serum.
• Found in normal humans and patients
with autoimmune diseases.
• These are capable of hydrolyzing proteins,
DNA, RNA, polysaccharides, etc.

39. Protabzymes And DNA Enzymes
• Natural abzymes with proteolytic activity are called Protabzymes.e.g.:
hydrolysis of specific proteins in patients with autoimmune diseases
such as bronchial Asthma multiple sclerosis.
• DNA hydrolyzing activity are called DNA abzymes.
• The pathogenic role of DNA abzymes is not quite clear. However they
act as a powerful regulator of apoptosis.

40. Examples For Abzymes
1. Hydrolysis of hydroxy ester by abzymes
• Hydroxy ester forms a cyclic intermediate during hydrolysis.
Cyclic phosphonate ester is the structural analog of the cyclic
intermediate.
• This analog is used as an antigen to elicit antibodies.
• These antibodies bind the cyclic intermediate, increasing the
reaction rate.

41. 2. Hydrolysis of ester by abzymes
• Ester forms a tetrahedral intermediate during hydrolysis.
• The phosphate analog of ester mimic this intermediate, used as
antigen to elicit antibodies.
• These antibodies recognize and bind to tetrahedral
intermediate and stabilize it resulting in rate acceleration.

42. Reactions Catalysed By Abzymes
1. Amide hydrolysis
2. Trans- Esterification
3. Photo cleavage
4. Photodimerization
5. Decarboxylation
6. Oxidation
7. Cyclization
8. Reduction of diketone
9. Hydrolysis of enol ethers

43. Applications of Abzymes
1. Synthesis of simple organic molecules.
2. Drug development.
3. Treatment of Cancer.
4. Treating allergy.
5. To treat viral and bacterial infection.

44. Potential HIV Treatment
• In June 2008 issue of the journal Autoimmunity Review, researchers of the
University of Texas Medical School at Houston announced that they have
engineered an abzyme that degrades the super-antigenic region of the
gp120 CD4 binding site.
• This is the one part of the HIV-virus outer coating that does not change,
because it is the attachment point to T-lymphocytes, the key cell in cell-
mediated immunity.
• Once infected by HIV, patients produce antibodies to the more changeable
parts of the viral coat. The antibodies are ineffective because of the virus’
ability to change their coats rapidly.

45. • Because this protein gp120 is necessary for HIV to attach, it does
not change across different strains and is a point of vulnerability
across the entire range of the HIV variant population.
• The abzyme does more than bind to the site, it catalytically destroys
the site, rendering the virus inert, and then can attack other HIV
viruses.
• A single abzyme molecule can destroy thousands of HIV viruses.

46. REFERENCE
• Satyanarayana, U., & Chakrapani, U. (2015). Biochemistry (with
clinical concepts & case studies). New Delhi: Elsevier Health
Sciences APAC.
• https://www.pathwayz.org/Tree/Plain/ENZYME+COFACTORS
• https://www.biovision.com/products/metabolism-
assays/coenzymes-cofactors.html
• https://www.wikidoc.org/index.php/Cofactor_(biochemistry)
• https://www.rgpv.ac.in/campus/PY/enzymes_ppt.pdf
• https://www.biologydiscussion.com/enzymes/study-notes-on-
abzymes-with-diagram/22960

47. THANK YOU