noun, plural: marker enzymes
Any enzyme confined to a particular organelle, cell, or cellular component
Marker enzymes are enzymes, which are not ubiquitous but confined to a specific type of organelle, a subcomponent, or a cell. Since marker enzymes are not to be found just anywhere else, their detection can indicate the presence of the source whereas their absence means the lack of that source.
Marker enzymes are one of the cell biomarkers used to characterize a cell type. They are also used in the isolation of the target cellular component.
For example, succinate dehydrogenase is a marker enzyme for mitochondrion whereas the acid phosphatase for lysozome.