A 40-year-old woman has a persistently elevated serum alkaline phosphatase. Electrophoretic separation is unavailable, so the sample is heated to 56 degrees Celsius for 10 minutes. Which result would support a BONE rather than a hepatic origin of the enzyme?
- A Almost all alkaline phosphatase activity is lost after heating ✓
- B More than 90% of alkaline phosphatase activity is retained after heating
- C Activity doubles after heating
- D Activity is unchanged whether heated or not
Correct answer: A. Almost all alkaline phosphatase activity is lost after heating
Explanation
Bone alkaline phosphatase is heat labile and is largely inactivated by heating at 56 degrees Celsius, whereas the liver isoenzyme is much more heat stable and retains activity even above 60 degrees Celsius. The placental isoenzyme is the most heat stable of all. This thermal stability difference is the classical bedside method for identifying the tissue source when electrophoresis is not available.
Reference: Harper's Illustrated Biochemistry, 31st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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