def enzymes_to_gpr_no_stoichiometry(rxn):
    """
    Builds a Gene to Protein to Reaction association rules from the enzymes of
    an enzymatic reaction

    :param rxn:
    :return:
    """
    return ' or '.join([' ( ' + ' and '.join([v
                                for v in isozyme.composition])  + ' ) '
                                for isozyme in rxn.enzymes] )