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Temperature dependence of macroamylase binding
Abstract:
The presence of macroamylasemia can be suspected when a patient has low renal clearance of amylase relative to creatinine (Cam/Ccr). However, the Cam/Ccr is seldom reduced to the extent expected given the fraction of amylase that appears to be bound in the macroamylase complex by gel filtration studies at 3 degrees C. Therefore, we tested the possibility that the binding of amylase in macroamylase complexes was temperature dependent and that binding at physiological temperatures might be less than at 3 degrees C. Gel filtration of five macroamylase-containing sera was carried out at temperatures of 3 degrees, 25 degrees, 37 degrees, 43 degrees, and 49 degrees C. Binding of amylase in the complex decreased as the temperature increased with virtually all amylase bound at 3 degrees C and virtually no amylase bound at 49 degrees C. The fraction of the amylase that bound at 37 degrees C was approximately what would have been predicted from the Cam/Ccr of each of the five subjects. We conclude that amylase binding in macroamylase complexes is extremely temperature sensitive and appreciable changes in binding may occur over the physiological temperature range of 37-41 degrees C.
Insights
Macroamylasemia, a condition with low amylase clearance, is temperature-dependent. Amylase binding in macroamylase complexes decreases significantly at higher temperatures, impacting renal clearance interpretations.
Area of Science:
- Biochemistry
- Clinical Chemistry
Background:
- Macroamylasemia is often suspected with low amylase to creatinine clearance ratio (Cam/Ccr).
- Observed Cam/Ccr is typically higher than expected based on in vitro amylase binding at 3°C.
Purpose of the Study:
- To investigate the temperature dependency of amylase binding in macroamylase complexes.
- To determine if reduced amylase binding at physiological temperatures explains discrepancies in Cam/Ccr.
Main Methods:
- Gel filtration of macroamylasemia sera at various temperatures (3°C to 49°C).
- Quantification of bound amylase within macroamylase complexes at each temperature.
Main Results:
- Amylase binding in macroamylase complexes significantly decreased with increasing temperature.
- Virtually no amylase was bound at 49°C, while nearly all was bound at 3°C.
- Amylase binding at 37°C correlated with predicted values based on subjects' Cam/Ccr.
Conclusions:
- Amylase binding in macroamylase complexes is highly temperature-sensitive.
- Physiological temperature fluctuations (37-41°C) can substantially alter amylase binding and affect Cam/Ccr interpretation.