title: Spectrophotometric assay for serum glutathione transferase: a re-examination.
abstract: OBJECTIVE
  The aim of the present paper is a careful re-examination of an automated spectrophotometric procedure for glutathione transferase (GST) activity in human serum described previously and used in many laboratories.
  
  
  METHODS
  GST activity in human serum has been assayed spectrophotometrically under various experimental conditions. Recombinant human GSTs and specific inhibitors were also used to check the possible occurrence of artifacts.
  
  
  RESULTS
  Basal level of the enzyme calculated using this method turns out to be much higher than that found using RIA and ELISA procedures. Relevant pH-dependent artifacts deeply affect this spectrophotometric assay. Notably, spectral changes previously interpreted as a measure of basal activity, are mainly due to an increase of the spontaneous reaction between the two substrates.
  
  
  CONCLUSIONS
  GST activity in normal serum cannot be correctly determined with the spectrophotometric assay described previously because of the very low enzyme concentration and the pH-dependent artifacts.
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, I-00133, Rome, Italy.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Fabrini
authors.forename: Alessio
authors.initials: A
authors.lastname: Bocedi
authors.forename: Renato
authors.initials: R
authors.lastname: Massoud
authors.forename: Giorgio
authors.initials: G
authors.lastname: Federici
authors.forename: Giorgio
authors.initials: G
authors.lastname: Ricci
mesh_terms: D016477:Artifacts; D001681:Biological Assay; D004795:Enzyme Stability; D004797:Enzyme-Linked Immunosorbent Assay; D005982:Glutathione Transferase / Q000097:blood*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007527:Isoenzymes / Q000097:blood; D011863:Radioimmunoassay; D011994:Recombinant Proteins / Q000097:blood; D013053:Spectrophotometry
chemical_list: D007527:Isoenzymes; D011994:Recombinant Proteins; D005982:Glutathione Transferase