Macroenzyme 1 is bound to what?

• A. Immunoglobulins
• B. Non-immunoglobulins
• C. Lipids
• D. Proteins

Answer: (A)

Macroenzymes form when a normal enzyme binds to a much larger molecule, which slows clearance from blood and can make routine assays show higher activity than clinically expected. Macroenzyme 1 is defined by being an enzyme bound to an immunoglobulin. This immunoglobulin association—most often with IgG—creates a high‑molecular‑weight complex that circulates longer and is not readily excreted by the kidneys, so the apparent enzyme activity remains elevated. Binding to immunoglobulins is the hallmark of this type; binding to lipids or other non-immunoglobulin proteins would describe other macroenzyme categories, not macroenzyme 1.