enzyme definition - help

[Harald Teicher]

[ Article crossposted from bionet.molbio.proteins ]
[ Author was Harald Teicher ]
[ Posted on 4 Mar 1996 12:02:09 GMT ]

Why are the photosynthetic elctron mediators Fd:NADPH oxidoreductase (FNR) and
the cytochrome b6-f complex (plastoquinol:plastocyanin oxidoreductase) class-
fied as enzymes, while plastocyanin (cyt f:P700 oxidoreductase) and ferredoxin
(Fa/Fb:FAD oxidoreductase) are not. 

I have posted this message to bionet.photosynthesis in a slightly longer ver-
sion, and received mixed responses: some  say Fd and Pc (and PSI and PSII)
are enzymes, others that Fd and Pc are too small to be enzymes, others that
proton (H+) transfer is an integral part of oxidoreductase activity.....

Any suggestions ? 

Thanks in advance:  Harry