Inhibition of murine N1-acetylated polyamine oxidase by an acetylenic amine and the allenic amine, MDL 72527.
Murine N(1)-acetylated polyamine oxidase (mPAO) was treated with N,N'-bis-(prop-2-ynyl)-1,4-diaminobutane, a poor substrate and inhibitor for the enzyme, with K(m) and K(i) 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,N'-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.
Wu
Tianyun
T
Molecular Biology Division, Department of Veterans Affairs Medical Center, San Francisco, CA 94121, USA.
Ling
Ke-Qing
KQ
Sayre
Lawrence M
LM
McIntire
William S
WS
D000107:Acetylation; D000818:Animals; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D005415:Flavins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D015394:Molecular Structure; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D011700:Putrescine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D013057:Spectrum Analysis; D014238:Trichloroacetic Acid / Q000494:pharmacology; D000097667:Polyamine Oxidase
D004791:Enzyme Inhibitors; D005415:Flavins; D000587:Oxidoreductases Acting on CH-NH Group Donors; D011700:Putrescine; D014238:Trichloroacetic Acid; D000097667:Polyamine Oxidase; C495171:N,N'-bis-(prop-2-ynyl)-1,4-diaminobutane; C044445:MDL 72527