Comparison of two methods for determining amylase activity in serum and urine.

E CLASSIC measurement of a-amylase (a1,4-glucan 4-glucanohydrolase, EC 3.2.1.1) activity in biological fluids is based on enzymatic hydrolysis of a starch substrate. This activity can be assessed either by a saccharogenic procedure (1, ), which measures the increase in reducing sugar (mainly maltose), or by an amyloclastic procedure (1, ), which depends on the decrease or disappearance of the blue color formed when iodine is added to starch. Various modifications of the original amyloclastic method (3-6) are routinely used in the clinical laboratories. Amyloelastic methods, though simple and quick, use suboptimal substrate concentrations, and are subject to error from the effect of protein (7), differences in starch from different sources (4), stability of substrate, and other factors. The new chromogenic amylase substrates recently reported (8-10) are claimed to be superior to starch substrates. Babson et at. (9) reported a substrate for amylase determination, based on the ability of Reactone Red-2B, a reactive dye, to bind to amylopectin in alkaline solution. Subsequently (ii), these workers claimed that their amylase method is superior to the Somogyi saccharogenic procedure, as well as being technically simpler. We here compare an amyloclastic method used