Abstract
Butyltin compounds were found to inhibit the activity of purified yeast glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in an in vitro system. The order of inhibitory effect, after tetrabutyltin, was dibutyltin, tributyltin and monobutyltin. The concentration of tetrabutyltin giving 50% inhibition of the yeast enzyme was 4.3×10-6 M. On the other hand, the activity of the human erythrocyte enzyme was inhibited only by tributyltin, but not by monobutyltin, dibutyltin or tetrabutyltin. The inhibition of glucose-6-phosphate dehydrogenase of yeast by tributyltin and tetrabutyltin could be prevented by the addition of bovine serum albumin, whereas the inhibition of the activity of the erythrocyte enzyme by tributyltin was not affected by bovine serum albumin. However, the addition of albumin to the once-inactivated enzyme did not restore the enzyme activity. Cysteine slightly protected the yeast enzyme from the inhibition by dibutyltin but did not affect the inhibitions by tributyltin and tetrabutyltin.
