Bruno Vecchi > Bio-Protease-1.112980 > Bio::ProteaseI



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Module Version: 1.112980   Source  


Bio::ProteaseI - A role to build your customized Protease


version 1.112980


    package My::Protease;
    use Moose;
    with 'Bio::ProteaseI';

    sub _cuts {
        my ($self, $peptide) = @_;

        # some code that decides
        # if $peptide should be cut or not

        if ( $peptide_should_be_cut ) { return 1 }
        else                          { return   }


This module describes the interface for Bio::Protease. You only need to use this if you want to build your custom specificity protease and regular expressions won't do; otherwise look at Bio::Protease instead.

All of the methods provided in Bio::Protease are defined here. The consuming class just has to implement a _cuts method.



Attempt to cleave $peptide at the C-terminal end of the $i-th residue (ie, at the right). If the bond is indeed cleavable (determined by the enzyme's specificity), then a list with the two products of the hydrolysis will be returned. Otherwise, returns false.

    my @products = $enzyme->cut($peptide, $i);


Performs a complete digestion of the peptide argument, returning a list with possible products. It does not do partial digests (see method cut for that).

    my @products = $enzyme->digest($protein);


Returns true or false whether the peptide argument is a substrate or not. Esentially, it's equivalent to calling cleavage_sites in boolean context, but with the difference that this method short-circuits when it finds its first cleavable site. Thus, it's useful for CPU-intensive tasks where the only information required is whether a polypeptide is a substrate of a particular enzyme or not


Returns a list with siscile bonds (bonds susceptible to be cleaved as determined by the enzyme's specificity). Bonds are numbered starting from 1, from N to C-terminal. Takes a string with the protein sequence as an argument:

    my @sites = $enzyme->cleavage_sites($peptide);

How to implement your own Protease class. ^

Step 1: create a class that does ProteaseI.

    package My::Protease;
    use Moose;
    with 'Bio::ProteaseI';


Simply create a new Moose class, and consume the Bio::ProteaseI role.

Step 2: Implement a _cuts() method.

The _cuts method will be used by the methods digest, cut, cleavage_sites and is_substrate. It will always be passed a string of 8 characters; if the method returns true, then the peptide bond between the 4th and 5th residues will be marked as siscile, and the appropiate action will be performed depending on which method was called.

Your specificity logic should only be concerned in deciding whether the 8-residue long peptide passed to it as an argument should be cut between the 4th and 5th residues. This is done in the private _cuts method, like so:

    sub _cuts {
        my ( $self, $peptide ) = @_;

        # some code that decides
        # if $peptide should be cut or not

        if ( $peptide_should_be_cut ) { return 1 }
        else                          { return   }

And that's it. Your class will be composed with all the methods mentioned above, and will work according to the specificity logic that you define in your _cuts() method.

Example: a ridiculously specific protease

Suppose you want to model a protease that only cleaves the sequence MAEL^VIKP. Your Protease class would be like this:

    package My::Ridiculously::Specific::Protease;
    use Moose;
    with 'Bio::ProteaseI';

    sub _cuts {
        my ( $self, $substrate ) = @_;

        if ( $substrate eq 'MAELVIKP' ) { return 1 }
        else                            { return   }


Then you can use your class easily in your application:

    #!/usr/bin/env perl
    use Modern::Perl;

    use My::Ridiculously::Specific::Protease;

    my $protease = My::Ridiculously::Specific::Protease->new;
    my @products = $protease->digest( 'AAAAMAELVIKPYYYYYYY' );

    say for @products; # ["AAAAMAEL", "VIKPYYYYYYY"]

Of course, this specificity model is too simple to deserve a new class, as it could be perfectly defined by a regex and passed to the specificity attribute of Bio::Protease. It's only used here as an example.


Bruno Vecchi <vecchi.b>


This software is copyright (c) 2011 by Bruno Vecchi.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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