Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.27 (thermolysin)
 1,894 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A single-sited iron-binding fragment of human transferrin has been obtained by thermolysin cleavage of the protein, selectively loaded with iron in the C-terminal binding site, in a urea-containing buffer. The fragment contains carbohydrate, and hence derives from the C-terminal half of transferrin. Its metal-binding site accepts Fe3+ and Cu2+ with bicarbonate as accompanying anion, but only Fe3+ with oxalate as anion. EPR spectroscopic properties of the fragment are similar to those of the corresponding site in the intact protein. However, iron-binding by the fragment is weaker than by the C-terminal site of the intact protein, particularly at low pH, suggesting that overall as well as local protein conformation influences the metal-binding functions of the site.
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PMID:Preparation and properties of a single-sited fragment from the C-terminal domain of human transferrin. 298 30

Dipeptidyl peptidase III (DPP III) (EC 3.4.14.4), which has a HELLGH-E (residues 450-455, 508) motif as the zinc binding site, is classified as a zinc metallopeptidase. The zinc dissociation constants of the wild type, Leu(453)-deleted, and E508D mutant of DPP III at pH 7.4 were 4.5 (+/-0.7) x 10(-13), 5.8 (+/-0.7) x 10(-12), and 3.2 (+/-0.9) x 10(-10) M, respectively. The recoveries of the enzyme activities by the addition of various metal ions to apo-DPP III were also measured, and Co(2+), Ni(2+), and Cu(2+) ions completely recovered the enzyme activities as did Zn(2+). The dissociation constants of Co(2+), Ni(2+), and Cu(2+) ions for apo-DPP III at pH 7.4 were 8.2 (+/-0.9) x 10(-13), 2.7 (+/-0.3) x 10(-12), and 1.1 (+/-0.1) x 10(-14) M, respectively. The shape of the absorption spectrum of Co(2+)-DPP III was very similar to that of Co(2+)-carboxypeptidase A or Co(2+)-thermolysin, in which the Co(2+) is bound to two histidyl nitrogens, a water molecule, and a glutamate residue. The absorption spectrum of Cu(2+)-DPP III is also very similar to that of Cu(2+)-thermolysin. The EPR spectrum and the EPR parameters of Cu(2+)-DPP III were very similar to those of Cu(2+)-thermolysin but slightly different from those of Cu(2+)-carboxypeptidase A. The five lines of the superfine structure in the perpendicular region of the EPR spectrum in Cu(2+)-DPP III suggest that nitrogen atoms should coordinate to the cupric ion in Cu(2+)-DPP III. All of these data suggest that the donor set and the coordination geometry of the metal ions in DPP III, which has the HExxxH motif as the metal binding site, are very similar to those of the metal ions in thermolysin, which has the HExxH motif.
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PMID:Characterization of the metal-substituted dipeptidyl peptidase III (rat liver). 1157 Aug 86

A recombinant rat aminopeptidase-B (Ap-B) was expressed as a glutathione S-transferase (GST) fusion protein in Escherichia coli BL21 harboring a plasmid pGEX-Ap-B and was purified by glutathione-Sepharose 4B and Q-Sepharose columns. The metal-substituted derivatives of Ap-B, Co(II)- and Cu(II)-Ap-B contain almost 1 mole of cobalt(II) and copper(II) ions per enzyme molecule, respectively. The specific activity of Co(II)-Ap-B is very similar to that of recombinant Ap-B but that of Cu(II)-Ap-B is very low. The dissociation constants of the zinc ions of recombinant Ap-B and of the cobalt ions of Co(II)-Ap-B calculated from the relationships between the free metal ions and the residual enzyme activities are 3.7(+/-1.0)x10(-13) and 4.7(+/-1.0)x10(-12) M, respectively. The EPR parameters (gperpendicular), g// and A//) of Cu(II)-Ap-B were 2.06, 2.27, and 156x10(-4) cm-1. The A// value and the g// of Cu(II)-Ap-B are very similar to those of Cu(II)-thermolysin or Cu(II)-dipeptidyl peptidase III, in which the coordination geometry is a distorted tetrahedral.
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PMID:Characterization of the metal-binding site in aminopeptidase B. 1714 67