1) Protein 
<biochemistry> An enzyme without its cofactor. ... See: apoprotein. ... (18 Nov 1997) ... 
(ap″o-en´zīm) the protein component of an enzyme that requires the presence of the prosthetic group (coenzyme) to form the functioning enzyme.
Enzyme lacking correct cofactor/coenzyme and hence unable to function correctlyAn enzyme without its cofactor. See apoprotein.
(apo) Type: Term Pronunciation: ap′ō-en′zīm Definitions: 1. The protein portion of an enzyme as contrasted with the nonprotein portion, coenzyme, or prosthetic portion (if present in the intact protein).
[n] - a protein that combines with a coenzyme to form an active enzyme
enzyme without its cofactor or coenzyme
noun a protein that combines with a coenzyme to form an active enzyme
the protein component that with a coenzyme forms a complete enzyme.