Properties of cobalt‐substituted bovine serum amine oxidase

Abstract

Half‐copper‐depleted and fully copper‐depleted amine oxidase from bovine serum were reconstituted with either copper or cobalt. All samples were studied by high‐sensitivity scanning calorimetry, by enzyme activity analysis, and by reactivity with phenylhydrazine. The calorimetric profile of the protein was strongly modified by the removal of a single Cu ion approximately to the same extent as by complete copper removal, in agreement with the loss of over 80% enzymic activity. The thermograms of metal‐reconstituted species showed a marked similarity with that of the native enzyme, irrespective of whether copper or cobalt was present. Reactivity with phenylhydrazine and enzymic activity measurements showed that in cobalt‐substituted amine oxidase the organic cofactor was reactive and the enzyme was catalytically competent, although kinetically less efficient. These observations agree both with previous findings on the protein half‐site reactivity and with previous suggestions for a copper conformational role in bovine serum amine oxidase, namely of maintaining a functional conformation at the active site. Copyright © 1994, Wiley Blackwell. All rights reserved