Related Experiment Video
Updated: Aug 15, 2025
Assaying for Inorganic Polyphosphate in Bacteria
Published on: January 21, 2019
Reference ranges for the polyethylene glycol (PEG) precipitation activity (%PPA) of eight routine enzyme activities
Carmen Bürki1, Martin Volleberg2, Linnea Blomgren3
1Medica Medizinische Laboratorien Dr. F. Kaeppeli AG, Zurich, Switzerland.
Abstract:
Macroenzymes are high-molecular weight forms of enzymes whose presence in human sera can lead to non-pathological, elevated enzyme activities, resulting in further unnecessary clinical evaluation. Precipitation with polyethylene glycol (PEG) is an efficient method for removing macroforms from patient samples and can therefore be used for their identification. Cut-offs (99. Percentiles) for the PEG precipitation activity (%PPA) for eight routine enzyme activities were determined on Abbott's Alinity c, namely: AST (61%), ALT (70%), GGT (41%), LDH (45%), lipase (56%), ALP (17%), CK (36%) and PAMY (45%). Two macroforms (PAMY and CK) were then identified by gel filtration chromatography. We suggest that a %PPA above the enzyme-specific cut-off makes the presence of a macroform possible while a %PPA ≥80%, i.e. markedly above the cut-off, makes it very likely for all enzymes.
Insights
Macroenzymes, high-molecular weight enzyme forms, can cause elevated activities. Polyethylene glycol (PEG) precipitation effectively identifies these macroenzymes, preventing unnecessary clinical evaluations.
Area of Science:
- Clinical Biochemistry
- Enzymology
- Diagnostic Medicine
Background:
- Macroenzymes are high-molecular weight enzyme variants found in human serum.
- Their presence can lead to falsely elevated enzyme activities, necessitating further investigation.
- Polyethylene glycol (PEG) precipitation is a recognized method for identifying macroenzyme forms.
Purpose of the Study:
- To establish cut-off values for PEG precipitation activity (%PPA) for routine enzymes.
- To assess the utility of %PPA in identifying macroenzyme presence.
- To validate macroenzyme identification using gel filtration chromatography.
Main Methods:
- Determined 99th percentile cut-offs for %PPA for eight enzymes (AST, ALT, GGT, LDH, lipase, ALP, CK, PAMY) using Abbott's Alinity c analyzer.
- Utilized gel filtration chromatography to confirm the presence of two macroforms (PAMY, CK).
Main Results:
- Established enzyme-specific %PPA cut-offs, ranging from 17% for ALP to 70% for ALT.
- Identified macro-PAMY and macro-CK using gel filtration chromatography.
- Proposed that %PPA above the enzyme-specific cut-off suggests macroenzyme presence, with %PPA ≥80% indicating high likelihood.
Conclusions:
- PEG precipitation provides a reliable method for detecting macroenzymes in patient samples.
- Defined %PPA cut-offs aid in distinguishing true enzyme elevations from those caused by macroenzymes.
- This approach can help avoid unnecessary clinical workups for non-pathological enzyme elevations.
