More info on the isoenzyme question

Ivano de Filippis ivano at ALPHA.INCQS.FIOCRUZ.BR
Tue Sep 9 12:45:14 EST 1997

At 17:59 03/09/97 GMT, you wrote:
>I had posted about use of the term isozyme.  Since I have gotten a few 
>questions about how "subtle" the structural differences are between forms, let 
>me just give some specifics.  I had hesitated on this to avoid possibly
>"blowing my cover"  as a reviewer.  The enzymes are the superoxide 
>dismutases (SODs).  Two of them have active sites which contain copper and 
>zinc, the other has an active site with manganese.  The MWs are quite 
>different for all 3, and antibodies to one generally don't react with the 
>other two.  Cells contain one of the Cu-Zn enzymes (mostly in the cytosol), 
>and the one Mn enzyme (in the mitochondria).  The other SOD is secreted to the 
>outside of cells and is called extracellular SOD.  Thus, these are three 
>structurally distinct enzymes which have a similar enzyme activity.
As I mentioned before (to your personal e-mail), if the three enzymes have
the same catalystic activities, they are isoenzymes [iso(functional)enzymes].


Ivano de Filippis
Fundacao Oswaldo Cruz - FIOCRUZ
Instituto Nacional de Controle de Qualidade em Saude - INCQS
Depto. de Microbiologia
Lab. de Materiais de Referencia
Av. Brasil, 4365 - Manguinhos
Rio de Janeiro - 21045-900 - BRASIL
Tel.: 55-21-598-4290/4291/4292/4293
FAX: 55-21-290-0915
E-mail: ivano at

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