Gamma-Glutamyl-3-carboxy-14-nitroanilide: the substrate of choice for routine determinations of gamma-glutamyl-transferase activity in serum?
Gamma-Glutamyl-3-carboxy-4-nitroanilide has been tested as donor substrate in the assay of gamma-glutamyltransferase activity in serum, glycylglycine being used as acceptor substrate. This donor substrate is highly solube even in neutral solutions, in contrast to the commonly used gamma-glutamyl-4-nitroanilide. The enzyme which apparently acts accordingly to a ping-pong bi bi kinetic mechanism, shows an absolute KM value for gamma-glutamyl-3-carboxy-4-nitroanilide of about 0.64 mmol/l, and for glycylglycine of about 13.4 mmol/l. The former KM value is significantly lower than that previously found for gamma-glutamyl-4-nitroanilide. The carboxyl derivative exhibits a marked competitive inhibitory effect on the gamma-glutamyltransferase. This effect is more pronounced than that of gamma-glutamyl-4-nitroanilide. The carboxyl derivative has somewhat higher absorbance in the range of wave length (400-420 nm) used to monitor the formation of the product. It is concluded that as donor substrate in the assay of gamma-glutamyltransferase activity of serum, the new derivative is not substantially superior to the gamma-glutamyl-4-nitroanilide conventionally used.
D015055:1-Carboxyglutamic Acid / Q000031:analogs & derivatives; D000813:Anilides; D005971:Glutamates; D006801:Humans; D007700:Kinetics; D008722:Methods; D013329:Structure-Activity Relationship; D005723:gamma-Glutamyltransferase / Q000097:blood*
D000813:Anilides; D005971:Glutamates; D015055:1-Carboxyglutamic Acid; C013540:gamma-glutamyl-3-carboxy-4-nitroanilide; D005723:gamma-Glutamyltransferase