A Simple Spectrophotometric Assay of Carboxypeptidase N (Kininase I) in Human Serum

A simple spectrophotometric assay of carboxypeptidase N (kininase I) in human serum.

Kininase I (carboxypeptidase N; EC 3.4.17.3) consists of carboxypeptidase N1 (CN1) and carboxypeptidase N2 (CN2); these two enzymes can be differentiated by their activities towards hippuryl-L-arginine and hippuryl-L-lysine, respectively. A spectrophotometric assay for both carboxypeptidases in human serum is described and the biochemical behaviour of these enzymes investigated. The pH optima a...

A labile enzyme in fresh human serum interferes with the assay of carboxypeptidase N.

Characterisation of a carboxypeptidase in human serum distinct from carboxypeptidase N.

Arginine carboxypeptidase activity in human serum, measured with the hippuryl-L-arginine substrate, is about three times higher than in human plasma. This difference is much smaller when hippuryl-L-lysine is used as the substrate. When fresh serum is incubated at 30 degrees C, the arginine and lysine carboxypeptidase activity decreases until a stable activity, close to the plasma activity, is r...

Simple spectrophotometric assay for measuring protein binding of penem antibiotics to human serum.

The binding of antibiotics to plasma (serum) proteins through hydrogen bonding can significantly influence the biological characteristics of these drugs. A rapid spectrophotometric assay has been developed that measures the level of free (unbound) penem antibiotic in serum ultrafiltrates. Whole human serum was adjusted to a standard concentration of antibiotic and then filtered by centrifugatio...

A simple spectrophotometric assay for arogenate dehydratase.

A simple spectrophotometric assay for arogenate dehydratase, the enzyme that catalyzes the formation of L-phenylalanine from L-arogenate, is presented. The method couples the arogenate dehydratase reaction with that of an aromatic aminotransferase partially purified from Acinetobacter calcoaceticus. In the presence of 2-ketoglutarate, phenylpyruvate formation is measured at 320 nm at basic pH. ...