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.
Weyler
W
W
Veterans Administration Medical Center, Molecular Biology, San Francisco, CA 94121.
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