THERMOSTABILITY OF PURIFIED HUMAN PANCREATIC ALPHA-AMYLASE IS INCREASED BY THE COMBINATION OF CA2-ALBUMIN( AND HUMAN SERUM)

Pancreatic fluid from a patient with a post operative pancreatic fistu la was used to isolate human a-amylase by means of acarbose affinity c hromatography. Amylase thermostability was measured in 4 solutions: (1 ) EDTA-dialyzed; (2) dialyzed solution plus 0.15 mmol/l (1.0 g/dl) hum an serum albumin; (3) dialyzed solution plus 0.25 mmol/l (1.0 mg/dl) c alcium ions; and (4) dialyzed solution with both human serum albumin a nd calcium ions. Amylase activity was measured at predetermined times in samples heated to 60 degrees C, Thermostability was characterized b y t(1/2), the time to 50% initial amylase enzyme activity. In the dial yzed solution t(1/2) was 0.75 +/- 0.19 min. This rose to 1.62 +/- 0.34 min with added human serum albumin, and to 8.24 +/- 0.13 min with add ed calcium ions. The combination of human serum albumin and calcium io ns resulted in a synergistic increase of t(1/2) to 180 +/- 26 min. The se findings support our contention that human serum albumin, calcium i ons and possibly other body fluid constituents must be considered in a ny utility involving amylase thermostability as a clinically relevant diagnostic marker.