Characterization of porcine alpha-class glutathione transferase A1-1 |
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Authors: | Fedulova Natalia Raffalli-Mathieu Françoise Mannervik Bengt |
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Institution: | aDepartment of Biochemistry and Organic Chemistry, Uppsala University, Biomedical Center, Box 576, SE-75123 Uppsala, Sweden;bDepartment of Neurochemistry, Stockholm University, SE-10691, Sweden |
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Abstract: | An Alpha-class glutathione transferase (GST) has been cloned from pig gonads. In addition to two conservative point mutations our nucleotide sequence presents a frame shift resulting from a missing A as compared to a previously published porcine GST A1-1 sequence. The deduced C-terminal amino-acid segment of the protein differs between the two variants. Repeated sequencing of cDNA isolated from different tissues and animals ruled out the possibility of a cloning artifact, and the deduced amino acid sequence of our clone showed higher similarity to related mammalian GST sequences. Hereafter, we refer to our cloned enzyme as GST A1-1 and to the previously published enzyme as GST A1-1∗. The study of the tissue distribution of the GSTA1 mRNA revealed high expression levels in many organs, in particular adipose tissue, liver, and pituitary gland. Porcine GST A1-1 was expressed in Escherichia coli and its kinetic properties were determined using alternative substrates. The catalytic activity in steroid isomerization reactions was at least 10-fold lower than the corresponding values for porcine GST A2-2, whereas the activity with 1-chloro-2,4-dinitrobenzene was approximately 8-fold higher. Differences in the H-site residues of mammalian Alpha-class GSTs may explain the catalytic divergence. |
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Keywords: | Sus scrofa Glutathione transferase A1-1 Alternative sequence Substrate selectivity |
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