Abstract
Binding of 4NQO to various kinds of enzymes or proteins was studied. Each one of proteins was mixed with 4NQO in 0.4 mM NaHCO3 solution and eluted through Ultrogel AcA 22 column. Radioactivity of 14C-labeled 4NQO found in protein fraction was measured. 4NQO bound hardly to polyglutamic acid and polyaspertic acid, somewhat to serum albumin, insulin, trypsin, RNA polymerase and DNA polymerase, and markedly to urease which is an SH enzyme. Lactate dehydrogenase, one of SH enzymes, aggregated with 4NQO. The binding of SH enzyme with the N-oxide would be attributable to a noncovalent binding such as ⟩N-O---H-S-, because 4NQO-urease binding yield markedly decreased in the presence of sodium dodecyl sulfate or cysteine, and also 4NQO-bound urease released 4NQO by the addition of sodium dodecyl sulfate.
