Gunji H, Kochi H, Hiraiwa K
Department of Legal Medicine, Fukushima Medical College, Japan.
Fukushima J Med Sci. 1994 Dec;40(2):119-32.
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.
对人精液γ-谷氨酰转移酶（GGT）进行了研究，测定了其初速度动力学、最适pH、受体特异性以及金属离子、EDTA和尿素的影响，并与人类肾GGT进行了比较。以甘氨酰甘氨酸为受体，γ-谷氨酰-4-硝基苯胺或γ-谷氨酰-3-羧基-4-硝基苯胺为供体来测定活性。由于双倒数图显示为平行线，精液GGT的反应以非顺序（乒乓双双）机制进行。以γ-谷氨酰-3-羧基-4-硝基苯胺和γ-谷氨酰-4-硝基苯胺为供体时，精液GGT的受体米氏常数比肾酶的约高2倍，而精液GGT的供体米氏常数与肾酶的非常相似。最适pH和pK值分别为8.2 - 8.6和约7.7。精液酶和肾酶对各种受体的特异性差异不大。除甘氨酰甘氨酸外，甘氨酰甘氨酰甘氨酸也是一种有效的受体，其活性为甘氨酰甘氨酸的80%。所测试的包括金属离子在内的各种底物对精液和肾GGT实际上既无抑制作用也无刺激作用。
