Comparison of kinetic property between human seminal and renal gamma-glutamyltransferase.
The initial-velocity kinetics, optimal pH, acceptor specificity and the influence of metal ions, EDTA and urea were studied on the human seminal gamma-glytamyltransferase (GGT) in comparison with the human renal GGT. The activity was measured with glycylglycine as an acceptor and with gamma-glutamyl-4-nitroanilide or gamma-glutamyl-3-carboxy-4-nitroanilide as a donor. Because the double-reciprocal plots showed paralled lines, the reaction of seminal GGT proceeds in nonsequence (Ping Pong Bi Bi) mechanism. The acceptor Michaelis constants for the seminal GGT were about 2 times higher than those for the renal enzyme with gamma-glutamyl-3-carboxy-4-nitroanilide as well as gamma-glutamyl-4-nitroanilide as donors, which the donor michaelis constants for seminal GGT were very similar to those for renal enzyme. The optimal pH and pK values were 8.2-8.6 and about 7.7, respectively. There was little difference in the specificity for various acceptors between the seminal and renal enzyme. Glycylglycylglycine was an effective acceptor other than glycylglycine, showing 80% of the activity with glycylgycine. Various substrates including metal ions tested were practically neither inhibitory nor stimulatory for seminal and renal GGTs.
Gunji
H
H
Department of Legal Medicine, Fukushima Medical College, Japan.
Kochi
H
H
Hiraiwa
K
K
D015055:1-Carboxyglutamic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D006033:Glycylglycine / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D012661:Semen / Q000201:enzymology*; D005723:gamma-Glutamyltransferase / Q000378:metabolism*
D006033:Glycylglycine; D015055:1-Carboxyglutamic Acid; C013540:gamma-glutamyl-3-carboxy-4-nitroanilide; D005723:gamma-Glutamyltransferase