Differential Effects of EDTA,Metal Ions,and Nucleotides on Glycoprotein Sialyltransferase Activity of Serum and Liver

Abstract

Summary

The effects of EDTA, divalent metal ions, and nucleotides on serum and liver glycoprotein sialyltransferase were studied. EDTA, at concentrations up to 16 mM, increased the transfer of [¹⁴C]NANA from CMP-[¹⁴C]NANA to desialyzed fe-tuin, by serum enzyme, while Mg²⁺ and Mn²⁺ at concentrations of 5-20 mM strongly inhibited the transfer. Nucleotides showed marked inhibitory effects on the transfer reaction. The extent of inhibition increased with the number of phosphate groups in the molecule. The enzyme in liver, on the other hand, required divalent metal ions for optimal activity. Also, UDP and UTP stimulated the enzyme in the liver.

This investigation was supported by NIH Grants Nos. HD-01823 and NS-11670. The authors wish to acknowledge the able technical assistance of Lora Nunes.