Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10772115 | Biochemical and Biophysical Research Communications | 2005 | 8 Pages |
Abstract
Murine N1-acetylated polyamine oxidase (mPAO) was treated with N,Nâ²-bis-(prop-2-ynyl)-1,4-diaminobutane, a poor substrate and inhibitor for the enzyme, with Km and Ki values in the millimolar range. Apparently, its oxidation produces prop-2-ynal, which reacts with amino acyl nucleophiles. Using a steady-state kinetic assay, four phases were identified, the first being the oxidation of the compound via Michealis-Menten-type kinetics. As prop-2-ynal accumulates, there is a biphasic reduction in the rate. This process leads to an mPAO form that is nearly inactive (fourth phase), but displays classical Michealis-Menten-type kinetics. The enzyme-bound flavin is not modified in this process. In contrast, micromolar concentrations of the MDL 72527 (N,Nâ²-bis-[buta-2,3-dienyl]-1,4-diaminobutane) inhibited mPAO rapidly and completely. It inhibits by first binding tightly and apparently irreversibly, and then slowly converts to a species where the inhibitor is covalently bound to the N5-position of the flavin's isoalloxazine ring. The covalent adduct was identified as a flavocyanine.
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Authors
Tianyun Wu, Ke-Qing Ling, Lawrence M. Sayre, William S. McIntire,