PURIFICATION, CHARACTERIZATION, AND CRYSTALLIZATION OF MONOAMINE-OXIDASE FROM ESCHERICHIA-COLI K-12

The gene for monoamine oxidase (MAO) was cloned from an Escherichia co li genomic library and MAO was overproduced in the periplasmic space. The enzyme was purified to homogeneity by preparation of a periplasmic fraction, followed by ammonium sulfate fractionation and DEAE-cellulo se column chromatography. Crystals were obtained by the hanging drop m ethod using sodium citrate as a precipitant. The enzyme was found to b e a dimer of identical subunits with a molecular weight of 80,000, and showed the highest activity at pH 7.5 and 45 degrees C. The enzyme wa s inhibited by a MAO specific inhibitor, hydroxylamine, hydrazine, phe nelzine, isoniazid, and tranycypromine. The enzyme oxidized tyramine, phenethylamine, and tryptamine at higher rates, but not oxidized diami ne and polyamines such as putrecine and spermine. The antibody against E. coli MAO cross-reacted with purified MAO A from Klebsiella aerogen es.