Bovine liver mitochondrial monoamine oxidase is not an iron-dependent enzyme.

M Ichinose,B Gomes,H Sanemori,K.T Yasunobu

doi:10.1016/s0021-9258(19)68281-5

Abstract

It has been reported that rat liver monoamine oxidase is an iron-dependent enzyme. Calculations from reported data suggest that rat liver monoamine oxidase contains 2 g atoms of iron/mol of enzyme. However, our data over a 16-year period show that our purified bovine liver monoamine oxidase does not contain sufficient iron to justify being considered an iron protein. In order to ensure the correctness of the iron content, two microchemical analyses and atomic absorption spectroscopy were used to determine the iron content of wet ashed samples. The iron content was also determined during successive steps of enzyme purification and was found to decrease rather than increase. Monoamine oxidase, being a hydrophobic outer membrane enzyme, is very difficult to purify and detailed tests for homogeneity are necessary. Our preparations show a single band when examined by sodium dodecyl sulfate-polyacrylamide disc electrophoresis and behave as a pure protein by end group analysis. Thus, bovine liver monoamine oxidase is not an iron-dependent enzyme.

Highlights

It has been reported that rat liver monoamine oxiddaissaegreement has prompted us to reinvestigate the iron quesis aniron-dependentenzyme.Calculationsfromretion with enzyme beingcurrently isolated
Methods used for protein two microchemical analyses andatomicabsorption determination, activity, and specific activity determinations are prespectroscopy of wet ashed mined during were used to determine the iron content samplesT. he iron contentwas detersuccessive steps of enzyme purification sented in the earlier reports
In the central nervous system, monoamine oxidase is pos- Determination of Iron Content during Enzyme Purificatulated to be important in controlling the levels of certain tion-If bovinelivermonoamineoxidasewere an iron-deneurohormones and other pharmacologically important pendent enzyme, the iron content of the enzyme would rise amines [1, 2]

Summary

THE JOURNALOF BIOLOGICALCHEMISTRY

Ported data suggest that rat liver monoamine oxidase contains 2 g atoms of iron/mol of enzyme. Our data over a 16-year period show that our purified Preparation of Enzyme-Prior to 1978,beeflivermonoamine bovine liver monoamine oxidase does not contain suf- oxidase was preparedbyprocedure I of Yasunobu et al [3]. Methods used for protein two microchemical analyses andatomicabsorption determination, activity, and specific activity determinations are prespectroscopy of wet ashed mined during were used to determine the iron content samplesT. Iron analysis wereperformed on wet ashed samples of enzyme which was firstdialyzed against 1 l ~ elthy~lenediamine tetraacetic acid, pH 7.4 and against 0.1 M Tris-HC1 buffer, pH 7.4. Theiron content of ashed samples polyacrylamide disc electrophoresis and behave as a of the enzyme was determinedby atomic absorptionspectroscopy pmuorneopamroitneeinobxyidaensedisgnrootupananiraolnys-dise. Model 290Batomic absorption were prepared by appropriate from pure iron wire

RESULTS

Ferrozine Atomic absorption SDeCtrODhOtOmetriC

DISCUSSION