Thornley-Brown D, Dass P D, Welbourne T C
Biochem Pharmacol. 1982 Nov 1;31(21):3347-52. doi: 10.1016/0006-2952(82)90610-4.
The effect of acetazolamide (AZ) on renal gamma-glutamyl transpeptidase (EC 2.3.2.2) activity (gamma-GT) was studied with the purified enzyme, subcellular fractions, and in the isolated functioning kidney. Activity of gamma-GT was assessed using either one of two gamma-glutamyl donors, gamma-glutamyl-p-nitroanilide (gamma GpNA) or glutamine, and either the gamma-glutamyl acceptor glycylglycine (Gly-Gly) or methionine (Met). With the microsomal enzyme and beta-GpNA, AZ was shown to inhibit p-nitroaniline (p-NA) formation; however, gamma-GpNA Km remained unchanged (1.8 mM), while the Vmax was reduced significantly, 333 vs 200 mumoles . min-1 . mg-1. Adding Gly-Gly removed AZ inhibition, while AZ elevated the apparent Km from Gly-Gly from 16 to 48; AZ inhibition of gamma-GT activity resulted in a decrease in gamma-glutamyl-Gly-Gly formation consistent with interaction at the gamma-glutamyl acceptor site. With glutamine as the beta-glutamyl donor, AZ reduced NH3 and apparent gamma-glutamylmethionine formation in the purified enzyme in agreement with inhibition at the acceptor site. In the functioning kidney, perfused with 10(-3)M L- or D-glutamine, AZ (10(-3)M) markedly reduced NH3 formation and increased glutamine excretion, results consistent with AZ inhibition of the in situ gamma-GT.
使用纯化的酶、亚细胞组分以及在离体的有功能的肾脏中研究了乙酰唑胺（AZ）对肾γ-谷氨酰转肽酶（EC 2.3.2.2）活性（γ-GT）的影响。使用两种γ-谷氨酰供体之一γ-谷氨酰-对硝基苯胺（γGpNA）或谷氨酰胺，以及γ-谷氨酰受体甘氨酰甘氨酸（Gly-Gly）或蛋氨酸（Met）来评估γ-GT的活性。对于微粒体酶和β-GpNA，显示AZ抑制对硝基苯胺（p-NA）的形成；然而，γ-GpNA的Km保持不变（1.8 mM），而Vmax显著降低，分别为333和200微摩尔·分钟⁻¹·毫克⁻¹。添加Gly-Gly可消除AZ的抑制作用，而AZ使Gly-Gly的表观Km从16升高至48；AZ对γ-GT活性的抑制导致γ-谷氨酰-Gly-Gly形成减少，这与在γ-谷氨酰受体位点的相互作用一致。以谷氨酰胺作为β-谷氨酰供体时，AZ减少了纯化酶中NH₃和表观γ-谷氨酰蛋氨酸的形成，这与在受体位点的抑制作用一致。在灌注10⁻³M L-或D-谷氨酰胺的有功能的肾脏中，AZ（10⁻³M）显著减少了NH₃的形成并增加了谷氨酰胺的排泄，结果与AZ对原位γ-GT的抑制作用一致。
