%0 Journal Article
%T Metal Preferences of Zinc-Binding Motif on Metalloproteases
%A Kayoko M. Fukasawa
%A Toshiyuki Hata
%A Yukio Ono
%A Junzo Hirose
%J Journal of Amino Acids
%D 2011
%I Hindawi Publishing Corporation
%R 10.4061/2011/574816
%X Almost all naturally occurring metalloproteases are monozinc enzymes. The zinc in any number of zinc metalloproteases has been substituted by some other divalent cation. Almost all Co(II)- or Mn(II)-substituted enzymes maintain the catalytic activity of their zinc counterparts. However, in the case of Cu(II) substitution of zinc proteases, a great number of enzymes are not active, for example, thermolysin, carboxypeptidase A, endopeptidase from Lactococcus lactis, or aminopeptidase B, while some do have catalytic activity, for example, astacin (37%) and DPP III (100%). Based on structural studies of various metal-substituted enzymes, for example, thermolysin, astacin, aminopeptidase B, dipeptidyl peptidase (DPP) III, and del-DPP III, the metal coordination geometries of both active and inactive Cu(II)-substituted enzymes are shown to be the same as those of the wild-type Zn(II) enzymes. Therefore, the enzyme activity of a copper-ion-substituted zinc metalloprotease may depend on the flexibility of catalytic domain. 1. Introduction Proteolytic enzymes are recognized by their catalytic type, that is, aspartic, cysteine, metallo, serine, threonine, and others as yet unclassified. The largest number of proteolytic enzymes are classified as metalloproteases [1]. Almost all metalloproteases contain one or two zinc ions, and several enzymes contain one or two cobalt or manganese ions. The HExxH motif forming an ¦Á-helix is well conserved in many monozinc enzymes as the active site in which the two histidine residues coordinate with the zinc ion [2]. Some other monozinc proteases have different zinc-binding motifs, for example, HxxE(D)-aan-H in the carboxypeptidase family or HxD-aa12-H-aa12-H in the matrix metalloprotease family [2]. Dipeptidyl peptidase (DPP) III also has a unique zinc-binding motif, which was classified as family M49 in 1999 by MEROPS (peptidase database) after rat DPP III had been cloned and the HELLGH motif of DPP III was identified as an active site coordinated with a zinc ion [3, 4]. Although the motif HELLGH could not be found in any other metalloproteases, it exists in three kinds of monooxygenases (tyrosine, phenylalanine, and tryptophan hydroxylases) as an iron-binding site, as revealed by a search of the NBRF-PIR protein sequence database. Zinc atoms in several zinc metalloproteases, for example, astacin [5], carboxypeptidase A [6], and thermolysin [7, 8], have been substituted by other divalent cations to probe the role of the metal for catalysis and structure. Some of these enzymes, for example, DPP III and astacin, were shown to
%U http://www.hindawi.com/journals/jaa/2011/574816/