Abzyme is a/an:

Abzyme is antibody acting as enzyme. It is a monoclonal antibody and is also called catalytic antibody or Catmab. Isozymes (Option 1): Physically distinct form of enzyme which catalyses same biochemical reaction. If species are different then isoenzymes are called alloenzymes. Allosteric enzymes (Option 4) or regulatory enzymes, unlike simple enzymes have regulatory/allosteric site ( other than the active site), where the regulator (activator/inhibitor) binds.