metalloenzyme

This term is a specialized technical noun used almost exclusively within biochemistry and molecular biology. It describes a specific class of proteins where the metal ion is not merely an accessory but a structural or catalytic necessity. In a laboratory or academic setting, the term implies a high degree of specificity regarding the enzyme's chemical composition.

Because it is a scientific classification, it is used in a neutral, descriptive register. It is rarely found in general conversation and typically appears in peer-reviewed journals, textbooks, or clinical reports to distinguish these proteins from non-metal-dependent enzymes.