title: Measurement of glyoxalase activities.
abstract: Glyoxalase I catalyses the isomerization of the hemithioacetal formed non-enzymatically from methylglyoxal and glutathione to S-D-lactoylglutathione. The activity of glyoxalase I is conventionally measured spectrophotometrically by following the increase in A240 for which the change in molar absorption coefficient Δε240=2.86 mM⁻¹·cm⁻¹. The hemithioacetal is pre-formed in situ by incubation of methylglyoxal and glutathione in 50 mM sodium phosphate buffer (pH 6.6) at 37°C for 10 min. The cell extract is then added, the A240 is monitored over 5 min, and the initial rate of increase in A240 and hence glyoxalase I activity deduced with correction for blank. Glyoxalase I activity is given in units per mg of protein or cell number where one unit is the amount of enzyme that catalyses the formation of 1 μmol of S-D-lactoylglutathione per min under assay conditions. Glyoxalase II catalyses the hydrolysis of S-D-lactoylglutathione to D-lactate and glutathione. Glyoxalase II activity is also measured spectrophotometrically by following the decrease in A240 for which the change in molar absorption coefficient Δε240=-3.10 mM⁻¹·cm⁻¹. It is given in units per mg of protein or cell number where one unit is the amount of enzyme that catalyses the hydrolysis of 1 μmol of S-D-lactoylglutathione per min under assay conditions. Glyoxalase I and glyoxalase II activity measurements have been modified for use with a UV-transparent microplate for higher sample throughput.
authors.forename: Makoto
authors.initials: M
authors.lastname: Arai
authors.forename: Naomi
authors.initials: N
authors.lastname: Nihonmatsu-Kikuchi
authors.affiliation: †Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo 156-8506, Japan.
authors.forename: Masanari
authors.initials: M
authors.lastname: Itokawa
authors.affiliation: *Clinical Sciences Research Laboratories, Warwick Medical School, University of Warwick, University Hospital, Coventry CV2 2DX, U.K.
authors.forename: Naila
authors.initials: N
authors.lastname: Rabbani
authors.affiliation: *Clinical Sciences Research Laboratories, Warwick Medical School, University of Warwick, University Hospital, Coventry CV2 2DX, U.K.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Thornalley
mesh_terms: D057075:Enzyme Assays / Q000379:methods*; D005978:Glutathione / Q000378:metabolism; D007791:Lactoylglutathione Lyase / Q000378:metabolism; D011765:Pyruvaldehyde / Q000378:metabolism
chemical_list: D011765:Pyruvaldehyde; D007791:Lactoylglutathione Lyase; D005978:Glutathione