Studies on the Xanthurenic Acid-Insulin Complex

Abstract

1. Xanthurenic acid(XA) and insulin readly combine on simple mixing of their solutions. 2. The complex shows a new absorption maximum at 327.5 mμ and this maximum is the same in position as that of a chelate compound of XA, zinc and histidine. 3. There are two moles of XA per dimer of insulin in the complex, so that the XA molecule probably combines with the imidazole group of a histidine residue of insulin via a zinc atom. 4. The specificity of the binding of XA to protein was studied.