the activity of adenosine 5'-phosphosulfate sulfotransferase activity decreases during cultivation with sulfate as the sole sulfur source, but after about 3 days it reaches a constant level (50 to 100 nmol activated sulfate transferred per h and mg protein) which is maintained for at least 24 h. Addition of 0.5 mM cysteine to the culture medium decreases adenosine 5'-phosphosulfate sulfotransferase activity and blocks growth completely
in Euglena, sulfate activation and reduction are contained in a sulfate metabolizing centre on the outside of the mitochondrial inner membrane. This centre appears to supply the mitochondrion and the rest of the cell with the products of sulfate activation as well as with the reduced sulfur in form of cysteine
thermal inactivation is depressed to a significant extent by a high concentration of Na2SO4. The effect is maximal in the concentration range of 0.4-0.6 M. Ammonium sulfate is effective as an inhibitor of the thermal inactivation, but NaC1, CH3COONa or NaNO3 is not. The thermal inactivation is also depressed to some extent by adenosine 5'-phosphosulfate or AMP. The effect is concentration-dependent up to at least 2.0 mM; thermal inactivation is depressed to a significant extent by a high concentration of Na2SO4. The effect is maximal in the concentration range of 0.4 M-0.6 M. Ammonium sulfate is also effective as an inhibtor of the thermal inactivation. Thermal inactivation is also depressed to some extent by adenosine 5'-phosphosulfate or its analogs, beta-methylene-adenosine 5'-phosphosulfate and AMP. The acceptor substrate dithiothreitol accelerates the thermal inactivation
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4°C, 50% of the activity is lost within 10 d, when the purified APSSTase is kept under N2 in 0.2M KH2PO4/K/HPO4 buffer (pH 8.0) containing 1.0 M (NH4)2SO4. The half-life for activity loss is slightly extended by the storage in an ice bath (0°C)