A Kinetic Photometric Method for Serum Leucine Aminopeptidase

Publisher Website
Google Scholar
Abstract
In this method L-leucyl-p-nitroanilide was used as substrate. The absorbance of the substrate at 405 m[mu] is negligible compared to that of the split product (p-nitroaniline), and there is the possibility for the direct kinetic determination. The incubation was directly performed in the cuvettes and the increase of the absorbance recorded. The activity was calculated from the angle formed between time axis and time-conversion-rate line. The maximal reaction velocity was found at pH 7.2. At 1.6 mM the optimal concentration of the substrate is still not obtained, but the limit of the solubility is reached. The enzymic activity was linear within a wide range of enzyme concentration and incubation time. At 25[degree]C incubation the normal range for women was between 9.8 - 20.5 mu and for men 10.1 - 22.9 m[mu]. The difference between sexes was significant. The method needs only 0.1 ml serum, is accurate and rapid. With an automatic cuvette positioner and recorder, up to 36 determinations can be performed in 1 hr.