| Abstract: |
A novel glutathione S-transferase (GST) was purified from broccoli (Brassica oleracea var. italica). Partial amino-acid sequencing indicated that the protein shared significant homology with several different plant GSTs from maize, silene, Dianthus, Nicotiana and Triticum, but little homology to yeast (Issatchenkia) [6] GST. One region of the polypeptide near the N-terminal also shared significant homology to a region of rat 5-5, rat 12-12 and human θ-GST (collectively referred to as the θ-GST-class) [7,8] but little structural homology to the common mammalian cytosolic GSTs (α-,μ- or π-classes) [9]. The broccoli GST was retained on a novel membrane based glutathione affinity matrix and displayed activity towards 1-chloro-2,4-dinitrobenzene (CDNB), a general GST substrate, as well as 4-nitrophenethyl bromide, a marker substrate for the θ-class of GSTs. The characteristics of the broccoli GST potentially define it as a member of the θ-class. This is consistent with the view that the θ-class may have arisen prior to the divergence of animals and plants while the mammalian μ-, π- and α-classes evolved after the two kingdoms were established. © 1994. |
