Effect of Cysteine on the Diazotization of Sulfanilamide in the Determination of Coenzyme A with Kaplan・Lipmann's Method

Abstract

The CoA determination by Kaplan and Lipmann^<1)>, is based on the fact that a bicarbonate extract of acetone-dried pigeon liver extract can acetylate sulfanilamide in the presence of ATP, CoA and acetate. The reaction is measured by noting the disappearance of sulfanilamide by the diazotization method of Bratton and Marshall. In the course of our studies on CoA determination, it was found that Cysteine had significantly reduced the diazotization of sulfanilamide, partly owing to insufficiency of sodium nitrite due to occurrence of so-called van Slyke reaction between sodium nitrite and Cysteine. The present communication also describes some improvements of the original diazotization procedures that bring about the reproducible and reliable results in CoA determination.