Simplification of a commercially available serum angiotensin-converting enzyme determination

The spectrophotometric method for the determination of angiotensin-converting enzyme in serum using p-hydroxyhippuryl-L-histidyl-L-leucine as substrate is commercially available as a test kit. It shows excellent linearity over the whole range of catalytic concentration found in serum. We describe several modifications of this method to simplify and economize the procedure.