Concept of ribozyme

2.  Definition
 History of Ribozyme discovery
 Characteristics of Ribozyme
 Structure and mechanism of Ribozyme
 Types of Ribozymes
 Applications

3.  Ribozymes (ribonucleic acid enzymes)
are RNA molecules that are capable of catalyzing
specific biochemical reactions, similar to the action of
protein enzymes.
 Discovery revealed that RNA contributed to the ‘RNA
world hypothesis’
 major role
a. Hydrolysis of phosphodiester bonds
b. Formation of bonds
c. Catalyze amino transferase activity of the
ribosome

4. • 1967 - Carl Woese, Francis Crick, and Leslie Orgel suggested
for the first time that RNA could act as a catalyst.
• 1970, Tomas R.Cech discovered the auto-splicing mechanism
of RNA molecule in Tetrahymena thermophila
• 1980s-T.R. Cech discovered catalytic RNAs
• 1982, Kelly Kruger coined the term ‘Ribozyme’ for these
catalytic RNA and published in “Cell”.
• mid-1980s Sidney Altman unraveled RNase P and its catalytic
role at University of Yale.
• 1989, T.R. Cech and S. Altman shared the Nobel Prize in
chemistry for their contributions in unraveling the catalytic
properties of RNA.
• 2001 "B6.61" could add up to 20 bases to a primer template

5.  Contrary to central dogma
 associated with metal ions
 Uses RNA as its substrate
 cleave other RNA molecules which
contained the NUX pattern of nucleotides
 Present in every living organism
 follows Michael-Menten kinetics

6.  diverse structures and mechanisms using the
four nitrogen base choices other than the
diverse amino acids for protein structure
Image showing diversity of ribozyme structure
(Leadzyme, hammer head, twister ribozymes)

7. • Capable of cleaving mRNA molecules in a sequence specific,
catalytic manner.
• They contain sequences for selective ligation, cleavage reaction
with target mRNAs.
• By modifying substrate recognising sequences , ribozyme can be
specifically tailored for the supression of particular geners

9. • involved in the
processing of
mRNA, tRNA &
rRNA.
• Splicing requires a
guanine residue
cofactor
• Self splicing by
trans esterification

11.  known as true RNAzyme
 A ribonucleoprotein, discovered around 40
years ago
 Mechanism of clevage is hydrolysis

12.  Tiny 30 nucleotide autocatalytic RNA
 It plays a role in reversible cleavage and joining
reactions at very specific site within RNA.
 Hammerhead ribozymes RNAs were discovered initially
in satellite RNAs and viroids (plant viruses.

13.  hepatitis delta virus (HDV) ribozyme
 85 nucleotide long, non coding
 plays role in viral replication. It is the only known
ribozyme required for the viability of a human
pathogen.
 VS or Varkud satellite ribozyme is the largest
known natural nucleolytic RNA
 satellite RNA is found in mitochondria of some
fungal strains like Neurospora

14.  small ribozymes found
in RNA satellites of
plant viruses.
 It assists in the
cleavage & ligation of
products of replication
to form circular and
linear satellite RNAs.

16.  Leadzyme- natural counterparts are in 5SrRNA.
 Ligase ribozyme- catalyse the assembly of RNA
fragments to form its polymer
 Allosteric ribozyme- act as molecular switches
 regulatory segment of a messenger RNA molecule that
binds a small molecule, resulting in a change in
production of the proteins encoded by the mRNA

18.  e-pathsala
 https://www.annualreviews.org/doi/full/10.1146/annurev.biophys.30.
1.457
 Slideshare.net
 https://www.news-medical.net/life-sciences/What-are-
Ribozymes.aspx
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