Effect of metal substitution in copper amine oxidase from lentil seedlings |
| |
Authors: | A Padiglia Rosaria Medda Jens Z Pedersen Alessandro Finazzi Agrò Anita Lorrai Barbara Murgia Giovanni Floris |
| |
Institution: | (1) Department of Sciences Applied to Biosystems University of Cagliari, I-09042 Cagliari, Italy e-mail: padiglia@unica.it Tel.: +39-070-6754515 Fax: +39-070-6754523, IT;(2) Department of Chemistry, Odense University, Odense Denmark, DK;(3) Department of Experimental Medicine, University of Rome "Tor Vergata", Rome, Italy, IT |
| |
Abstract: | The reaction with substrates and carbonyl reagents of native lentil Cu-amine oxidase and its modified forms, i.e. Cu-fully-depleted,
Cu-half-reconstituted, Cu-fully-reconstituted, Co-substituted, Ni-substituted and Zn-substituted, has been studied. Upon removal
of only one of the two Cu ions, the enzyme loses 50% of its enzymatic activity. Using several substrates, Co-substituted lentil
amine oxidase is shown to be active but the k
c value is different from that of native or Cu-fully-reconstituted enzyme, while K
m is similar. On the other hand, the Ni- and Zn-substituted forms are catalytically inactive. Enzymatic activity measurements
and optical spectroscopy show that only in the Co-substituted enzyme is the organic cofactor 6-hydroxydopa quinone reactive
and the enzyme catalytically competent, although less efficient. The Co-substituted amine oxidase does not form the semiquinone
radical as an intermediate of the catalytic reaction. While devoid or reduced of catalytic activity, all the enzyme preparations
are still able to oxidise two moles of substrate and to release two moles of aldehyde per mole of dimeric enzyme. The results
obtained show that although Co-substituted amine oxidase is catalytically competent, copper is essential for the catalytic
mechanism.
Received: 5 March 1999 / Accepted: 22 July 1999 |
| |
Keywords: | Lens esculenta Lentil Cofactor Copper 6-Hydroxydopa |
本文献已被 SpringerLink 等数据库收录! |
|