Monoamine oxidase A from human placenta and monoamine oxidase B from bovine liver both have one FAD per subunit

• Published in: Biochemical journal Vol. 260; no. 3; pp. 725 - 729
• Main Author: Weyler, W
• Format: Journal Article
• Language: English
• Published: England 15-06-1989
• Subjects: Amino Acids - isolation & purification; Animals; Cattle; Female; Flavin-Adenine Dinucleotide - isolation & purification; Humans; Isoenzymes - isolation & purification; Liver - enzymology; man; Monoamine Oxidase - isolation & purification; Placenta - enzymology; Pregnancy
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2600725

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.