Monoamine oxidase A from human placenta and monoamine oxidase B from bovine liver both have one FAD per subunit.
I present the first clear evidence that the protein: FAD ratio in human monoamine oxidase A and bovine monoamine oxidase B has an upper limit of 65 kDa and 57 kDa per FAD, respectively. To now it had been assumed that the protein: FAD ratio was 100-120 kDa to 1 FAD and that there was one FAD per two subunits which were assumed to be of the same size. For the present work the purity of monoamine oxidase A and monoamine oxidase B was improved over that previously achieved. Protein was determined by quantitative amino acid analysis and FAD content was measured by spectrophotometric titration of SDS-denatured enzyme with NaS2O4 standardized against riboflavin. The cause of the previous misassignment of the protein: FAD ratio was judged as having been due to the use of impure enzyme preparations. Knowledge of the correct protein: FAD ratio is important in devising cloning strategies for this enzyme, in understanding its structure, function, mechanism, and in the studies of its biosynthesis.
Veterans Administration Medical Center, Molecular Biology, San Francisco, CA 94121.
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Weyler
D000596:Amino Acids / Q000302:isolation & purification; D000818:Animals; D002417:Cattle; D005260:Female; D005182:Flavin-Adenine Dinucleotide / Q000302:isolation & purification*; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification*; D008099:Liver / Q000201:enzymology*; D008995:Monoamine Oxidase / Q000302:isolation & purification*; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy
D000596:Amino Acids; D007527:Isoenzymes; D005182:Flavin-Adenine Dinucleotide; D008995:Monoamine Oxidase