Inhibitor Proteins - Enzyme-activity Control
One kind of inhibitor protein found in higher plants is an endopeptidase which degrades nitrate reductase thus causing irreversible loss of the enzyme. The other kind includes binding proteins that specifically bind to nitrate reductase leading to permanent inactivation of enzyme. Such inactivator proteins have been isolated from rice seedings and spinach leaves. You will see that the transcription of enzyme is mediated by light. It is unique enzyme in this respect.