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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