| Abstract: | Bovine lactoperoxidase (LPO) gradually lost its enzymatic activity when dialyzed against a solution of 3-amino-1:2:4-triazole (AT) and hydrogen peroxide at pH 7.0. Amino acid analysis of the completely inactive enzyme revealed the formation of a new ninhydrin-positive chromatographic peak. This peak which had been observed previously when catalases were similarly reacted with AT in the presence of hydrogen peroxide is attributed to the covalent reaction product of AT with a histidyl residue. Concurrently with the appearance of the new ninhydrin-positive peak, the histidine content of LPO decreased by approximately two residues. Four to five residues of tyrosine were also lost. |
