A mu-class glutathione S-transferase from gills of the marine shrimp Litopenaeus vannamei:: Purification and characterization

Glutathione S-transferases (GSTs) are a family of detoxifying enzymes that catalyze the conjugation of glutathione (GSH) to electrophiles, thereby increasing the solubility of GSH and aiding its excretion from the cell. In this study, a glutatione S-transferase from the gills of the marine shrimp Litopenaeus vannamei was purified by affinity chromatography using a glutathione-agarose affinity column. GST was purified to homogeneity as judged by reducing SDS-PAGE and zymograms. This enzyme is a homodimer composed of similar to 25-kDa subunits and identified as a Mu-class GST based on its activity against 1-chloro-2,4-dinitrobenzene (CDNB) and internal peptide sequence. The specific activity of purified GST was 440.12 mu mol/(min mg), and the K-m values for CDNB and GSH are very similar (390 and 335 mu M, respectively). The intersecting pattern of the initial velocities of this enzyme in the Lineweaver-Burke plot is consistent with a sequential steady-state kinetic mechanism. The high specific activity of shrimp GST may be related to a highly effective detoxification mechanism necessary in gills since they are exposed to the external and frequently contaminated environment. (c) 2007 Wiley Periodicals, Inc.