A macroenzyme is a large circulating complex of enzyme molecules with something else, often an autoantibody. The individual enzyme molecules are not cleared as quickly so there is an accumulation of enzyme activity to a new plateau level.
Clinical features of a macroenzyme:
(1) persistent elevation in an enzyme's activity
(2) absence of an underlying disease that can explain the elevation
(3) presence of a condition associated with the formation of a macroenzyme (usually an autoimmune disease but also infusion of hydroxyethyl starch or lipid aggregates)
(4) demonstration of a macroenzyme (see next)
A macroenzyme can be demonstrated by:
(1) protein electrophoresis
(2) gel filtration chromatography
(3) testing before and after polyethylene glycol precipitation
(4) testing before and after mixing with immunoglobulin binding with protein G or protein A- Sepharose beads (for autoantibody-based macroenzymes)
