proteases as drug target
TRANSCRIPT
PROTEASES AS DRUG TARGET (MEROPS)
Presented By:
Mahmmoud Adel Mahmmoud
&
Adelegan Adebukola
INTRODUCTION
Proteases (aka Peptidases or Proteolytic enzymes) catalyze the
breakdown of protein peptide bonds.
Proteolysis is an irreversible regulatory mechanism and are known to
selectively cleave specific substrates
Deregulated modifications in proteolytic actions underlie many diseases like
cancer,neurodegenerative and cardiavascular disorders.
With strong evidence of protease involvement in diseases,proteases play an
important role in Drug development.
MEROPS is a database that contains the classification and Nomenclature of
proteolytic enzymes with their inhibitors.
The database includes a collection of known cleavage sites in Substrates.
The knowledge of cleavages in proteins,peptide and synthetic substrates is
important for understanding the specificity and physiological roles of
Proteolytic enzymes.
MEROPS
In 1993, Rawlings and Barret described a system in which individual
peptidases were assigned to families and the families grouped into clans.
The scheme was developed to provide the structure of the MEROPS
database .
The database was developed at Babraham University and moved to the
wellcome Trust Sanger Institute in 2002
The database contains about more than 2000 peptidases and nearly 400
inhibitors.
The peptidases and their inhibitors are classified into Families and Clans.
The protein to which each peptidase or inhibitor belongs which has been
fully characterized biochemically is chosen as a representative called
‘Holotype’
CLASSIFICATION OF PROTEASES
Three useful methods of grouping Preoteases are currently in use:
By the chemical mechanism of catalysis.
E.g: Serine catalytic type, Aspartic and Threoninine catalytic types.
Proteolytic enzymes grouped by the type of reaction they catalyze
E.g: Endopeptidases and Exopeptidases.
By molecular structure and Homology
This depends on the availability of Data for Amino acid sequences and the
3D structures.
SERINE PEPTIDASES
Serine serves as the nucleophilic amino acid at the at the catalytic site f the enzyme.serine peptidase has an –OH group that is able to act as a nucleophile attacking carbonyl Carbon of the peptide bond of the substrate.
There are the trypsin like proteases which cleaves following a positively charged amino acid.
And the Chymotrypsin-like which cleaves medium to large sized Hydrophobic amino acid such as Y, F and W.
Inhibition: Serine proteases are paired with serine protease inhibitors which turns off their activities when not needed.
Examples:
Kallikrein is involved in blood coagulation and is inhibted by Antithrombin
Neutrophyl elastase ,an enzyme of inflammatory cells that can cause damages to tissues is inhibited by Alpha-1 antityrpsin
Bacterial serine proteases are inhibited by B lactams
ASPARTIC PEPTIDASES
These use aspartate residue for catalysis of their peptide substrates
In generalthey have two(2)highly conserved aspartates in the active site.
Members of this class include,Pepsins and Renins
They are optimally active at acidic pH
Inhibition:
HIV - 1 retropepsin which is a drug target for HIV treatment
ACE is a target for renin inhibitor in the treatment of hypertension.
Pepstatin is a good inhibitor of aspartic proteases
Pepstatin binding to the active site of an
aspartic protease.
METALLO PEPTIDASES
These are protease enzymes whose catalytic mechanism involves a metal.
Most require Zinc but some cobalt
The metal ion is coordinated to the protein via three ligands which vary with
Histidine,Glutamate,Aspartate,Lysine and Arginine.
Inhibition:
Aminopeptidase N which plays a role in tumor invasion and metastatis is
inhibited by Antineoplaston AS2–5,a metallo protease inhibitor.
Generally metallo peptidases can be inhibited by chelating agents such as
EDTA and
Orthophenanthroline
CYSTEINE PEPTIDASES
Also known as Thiol proteases.
Catalyzes hydrolyis of peptide bonds by deprotonation of the thiol in the
enzyme’s active site by an adjacent amino acid with a basic side chain
usually Histidine.
Inhibition:
Cathepsin k inhibitor shows great potential in the treatment of Osteoporosis.
Cathepsin D inhibitor essential in breast cancer treatment
THREONINE PEPTIDASE
These peptidases are said to be involved in Malaria (Plasmodial
threonine pepetidases)
Inhibition:
pfHsIV a threonine peptidase is claimed to be an attractive drug
target for Malaria treatment
Investigation is required to clarify it’s functional role in the parasite.
COMPOUND PEPTIDASE
More than one peptidase unit exist within the protein molecule.
An example is Polyserase 1 which is involved in tumor formation
Inhibition:
Proteolytic activities of Polyserase1 units which is involved in tumor
formation is said to be inhibited by serine-protease inbibitors
Proteasomes:
(Ubiquitin-proteasome system)
Degradation of unneeded or damaged proteins by proteolysis ; (a chemical reaction that breaks peptide bonds and
catalysed by proteases enzymes).
Importance:
1. In the cell cycle control
2. Regulation of gene expression
3. In the response to oxidative stress
Protease Inhibitors:
1. Ritonavir (Norvir): anti-HIV Drug
Inhibition of HIV Virus Infection (Prevent AIDS disease).
Mechanism of Action:
Inhibition of retroviral aspartyl protease Enzyme (retropepsin) that is important in the replication and assembly of the new virions.
Ritonavir bound to the HIV proteases
2- Bortezomib (Velcade): anti-tumor Drug
In treating Multiple Myeloma and prostatic cancers.
Mode of Action:
a) Bind to 26S proteasome Inhibit degradation of pro-apoptotic factors activating apoptosis.
b) Inhibit IkBα degradation preventing NFkB from tanscriping genes encoded for growth, angeogensis and anti-apoptotic factors.
SUMMARY Therapies have been formulated to target and inhibit proteases
that are disregulated,especially for tumor suppresssion
Protease inhibitors have shown success in treatment of
haematological malignancies and have therefore been tested as
therapeutic agents in clinic for over 10 years.
With a brief introduction to the classes of proteases in
human,we have been able to show tha their disregulion can be
implicated in many forms of cancer as well as
neurological,pulmonary and cardiovascular diseases
The MEROPS database aims to fulfil the need for an integrated
source of information about the peptidases,their substrates and
inhibitors
The database has hierarchical classification in which
homoogous sets of peptidases and protein inhibitor are
grouped into protein species,whch are grouped into families
and further grouped into clans.
REFERENCES Barret AJ,Rawlings ND. Species of peptidases. Biol.
Chem 2007
Rawlings ND,Barret AJ, Merops.The peptidase
database.
Lopez-Otin C,Bond Js.Proteases:Multifunctional
enzymes in life and diseases
Orlowski RZ, Kuhn DJ. Proteosome inhibitors in
cancer therapy
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