Meprins are @entity1 @entity219 metalloendopeptidases with protease domains structurally related to @entity21877 , the prototype of the " @entity21877 family" of metalloproteases. Mature, active astacins are produced by proteolytic removal of an activation peptide to generate a new @entity2733 -terminal residue. Structural studies indicate that the @entity2733 -terminal @entity3104 group inserts into a water-filled cavity adjacent to the active site to form a salt bridge with a @entity367 residue that is conserved in all astacins. A similar interaction is known to play a crucial role in the activation of trypsin, resulting in the hypothesis that this salt bridge is required for the activation of @entity21877 -like proteases. In this study, we have used the @entity19 @entity70006 subunit as a model to test this hypothesis of zymogen activation of the astacins. Mutants were generated to vary the @entity2733 -terminal residue of the mature @entity70006 subunit ( @entity2734 78) and its putative salt bridge partner ( @entity367 178). In addition, mutants creating @entity2733 -terminal extensions and truncations were expressed in @entity1 embryonic kidney 293 cells. The recombinant proteins were activated by limited protease digestion and assayed for enzymatic activity and thermal stability. Point mutations of @entity2734 78 resulted in enzymes with activity comparable to the wild-type enzyme, indicating that the structure of this side chain is not essential for activity. @entity2733 -terminal extension mutants of @entity70006 retained partial activity, with greater decreases against peptide relative to protein substrates. A mutant with a deletion of @entity2734 78 to disrupt salt bridge formation with @entity367 178 had full activity, indicating that the putative salt bridge with @entity367 178 is not essential for enzyme activity. However, all changes in @entity70006 subunit @entity2733 -terminal structure were found to decrease the thermal stability of the enzyme. These observations and additional data indicate that the zymogen activation mechanism of meprin and other astacins differs from that of the trypsin family of enzymes, and has some features in common with matrixins. It is proposed that prosequence removal of astacins allows the formation of @entity3884 bonds involving the two @entity2733 -terminal residues that are critical for enzyme structure.

Activation mechanism of meprins, members of the XXXX metalloendopeptidase family.

@entity1 :: ('9606', 'Species') :: ['mammalian', 'human'] @entity21877 :: ('CHEBI:35327', 'Chemical') :: ['astacin'] @entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity19 :: ('10090', 'Species') :: ['mouse'] @entity219 :: ('MESH:D015032', 'Chemical') :: ['zinc'] @entity2734 :: ('CHEBI:17196', 'Chemical') :: ['Asn'] @entity2733 :: ('CHEBI:29345', 'Chemical') :: ['NH2'] @entity367 :: ('CHEBI:18237', 'Chemical') :: ['Glu'] @entity3104 :: ('MESH:D000644', 'Chemical') :: ['ammonium'] @entity70006 :: ('17287(Tax:10090)', 'Gene') :: ['meprin alpha']
@entity21877 :: (CHEBI:35327,Chemical) :: ['astacin']
