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 ∼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 μmol/(min mg), and the K m values for CDNB and GSH are very similar (390 and 335 μM, 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. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:62–67, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20162