L-ascorbic acid 2-sulphate. A substrate for mammalian arylsulphatases

Area of Science:

• Biochemistry
• Enzymology

Background:

• Ascorbic acid 2-sulphate stability in acidic conditions is comparable to phenyl sulphate.
• It is more acid-labile than simple carbohydrate sulphates.

Purpose of the Study:

• To investigate the enzymatic hydrolysis of ascorbic acid 2-sulphate by sulphatase A and B.
• To characterize the kinetics and inhibition patterns of these enzymes with ascorbic acid 2-sulphate.

Main Methods:

• Enzyme kinetics assays were performed for sulphatase A and B using ascorbic acid 2-sulphate as a substrate.
• The effect of potassium sulfate (K2SO4) as a competitive inhibitor was evaluated.
• Enzyme activity was measured at different pH values and salt concentrations.

Main Results:

• Sulphatase A efficiently hydrolyzes ascorbic acid sulphate with specific activity of 90 µmol/mg/min at pH 4.8.
• Non-Michaelis kinetics were observed for sulphatase A at pH 4.8, while Michaelis kinetics were observed at pH 5.6 (Km 12-21 mM).
• Sulphatase B also hydrolyzes ascorbic acid 2-sulphate, with activity significantly decreased in the absence of NaCl (Km 8 mM).
• Potassium sulfate competitively inhibits both enzymes.
• Ascorbic acid is not hydrolyzed by arylsulphatases from Dicathais orbita or Aerobacter aerogenes.

Conclusions:

• Sulphatase A and B are capable of hydrolyzing ascorbic acid 2-sulphate, exhibiting distinct kinetic properties and inhibition profiles.
• Enzyme activity is influenced by pH and salt concentration.
• The findings contribute to understanding the enzymatic metabolism of ascorbic acid derivatives.