Modulation of testicular galactolipid sulfotransferase activity in vitro by ATP

Testicular galactolipid sulfotransferase activity is an early marker of differentiation during mammalian spermatogenesis. The enzyme will catalyze the sulfation of galactosylglycerol in the 3' position of the galactose moiety at 37 degrees C in vitro. However, sulfotransferase activity was found to be completely lost on preincubation of the solubilized enzyme preparation at 37 degrees C. This loss of activity was completely prevented by inclusion of ATP and Triton in the preincubation step. This protective effect was synergistic, pH dependent and correlated with an inhibition of endogenous phosphatase activity. These results are interpreted to suggest that the galactolipid sulfotransferase may be regulated by a phosphorylation mechanism.