Pyridoxal 5′-phosphate binds to a lysine residue in the adenosine 3′-phosphate 5′-phosphosulfate recognition site of glycolipid sulfotransferase from human renal cancer cells

Abstract

In the course of characterization of glycolipid sulfotransferase from human renal cancer cells, the manner of inhibition of sulfotransferase activity with pyridoxal 5′-phosphate was investigated. Incubation of a partially purified sulfotransferase preparation with pyridoxal 5′-phosphate followed by reduction with NaBH₄ resulted in an irreversible inactivation of the enzyme. When adenosine 3′-phosphate 5′-phosphosulfate was co-incubated with pyridoxal 5′-phosphate, the enzyme was protected against this inactivation. Furthermore, pyridoxal 5′-phosphate was found to behave as a competitive inhibitor with respect to adenosine 3′-phosphate 5′-phosphosulfate with aK _i value of 287 µm. These results suggest that pyridoxal 5′-phosphate modified a lysine residue in the adenosine 3′-phosphate 5′-phosphosulfate-recognizing site of the sulfotransferase.