Excess substrate inhibition of xanthine oxidase: a reexamination

Abstract

Xanthine oxidase has long been considered to be subject to inhibition by excess substrate. It is now shown that, although such inhibition can be seen in Tris or N,N-bis(2-hydroxyethyl)glycine buffers, earlier reports in which phosphate, pyrophosphate, or Veronal buffers were used were probably the result of a spectrophotometric artifact imposed by stray light in the incident beam.