Studies on the Subunits of Rabbit Hepatic Glutathione S-Transferases

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We previously reported that the purified glutathione S-transferases from rabbit liver are homodimers or heterodimers of four different subunits, having molecular weight of 24500 (Y1), 25000 (Y2), 26500 (Y3)and 28000(Y4). Their subunit compositions were also reported to be Y1Y1 (R1a), Y1Y3 (R3a), Y3Y3 (R3b), Y2Y2 (R2) and Y2Y4 (R1b, R1c, R1d).In the present study, two additional isozymes, R3o and R3c, were obtained. They showed the same subunit compositions as R1a and R3b, respectively. Each subunit with the same molecular weight among different isozymes was demonstrated to have the same pI value by isoelectric focusing on polyacrylamide-gel plates containing 7.5 M urea (Y1,pI 8.49; Y2,pI 7.86; Y3,pI 8.41; Y4,pI 7.15). R3a (Y1Y3) in a reconstitution experiment using 4 M guanidine hydrochloride gave Y1Y1 homodimer (R3o), Y1Y3 heterodimer (R3a) and Y3Y3 homodimer (R3b). Similarly, the reconstituted R1c (Y2Y4) gave Y2Y2 homodimer (R2), Y2Y4 heterodimer (R1c) and an isozyme which probably has the subunit composition of Y4Y4. The failure of the in vitro formation of heterodimers such as Y1Y2,Y1Y4,Y2Y3 and Y3Y4 suggests that the possible combinations of subunits are limited.
公益社団法人日本薬学会の論文
1988-11-25