Gilead Sciences and IOCB Research Centre, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic; Department of Biochemistry, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
Prostate. 2014 May;74(7):768-80. doi: 10.1002/pros.22796. Epub 2014 Mar 20.
Glutamate carboxypeptidase II (GCPII) is a transmembrane enzyme that cleaves N-acetyl-L-aspartyl-L-glutamate (NAAG) in the brain. GCPII is highly expressed in the prostate and prostate cancer and might be associated with prostate cancer progression. Another exopeptidase, plasma glutamate carboxypeptidase (PGCP), was reported to be similar to GCPII and to share its NAAG-hydrolyzing activity.
We performed a radioenzymatic assay with [(3) H]NAAG as a substrate to detect and quantify the enzymatic activity of GCPII in plasma. Using a specific antibody raised against native GCPII (2G7), we immunoprecipitated GCPII from human plasma. We also cloned two PGCP constructs, expressed them in insect cells, and tested them for their NAAG-hydrolyzing activity.
We detected GCPII protein in human plasma and found that its concentration ranges between 1.3 and 17.2 ng/ml in volunteers not diagnosed with prostate cancer. Recombinant PGCP was enzymatically active but exhibited no NAAG-hydrolyzing activity.
GCPII is present in human blood, and its concentration within a healthy population varies. Recombinant PGCP does not hydrolyze NAAG, suggesting that GCPII alone is responsible for the NAAG-hydrolyzing activity observed in human blood. The potential correlation between GCPII serum levels and the disease status of prostate cancer patients will be further investigated.
谷氨酸羧肽酶 II（GCPII）是一种跨膜酶，可在大脑中切割 N-乙酰-L-天冬氨酰-L-谷氨酸（NAAG）。GCPII 在前列腺和前列腺癌中高度表达，可能与前列腺癌的进展有关。另一种外肽酶，血浆谷氨酸羧肽酶（PGCP）被报道与 GCPII 相似，并具有共享的 NAAG 水解活性。
我们使用 [(3) H]NAAG 作为底物进行放射酶测定，以检测和定量人血浆中 GCPII 的酶活性。使用针对天然 GCPII（2G7）的特异性抗体，我们从人血浆中免疫沉淀 GCPII。我们还克隆了两种 PGCP 构建体，在昆虫细胞中表达它们，并测试它们的 NAAG 水解活性。
我们在人血浆中检测到 GCPII 蛋白，并发现未被诊断患有前列腺癌的志愿者中其浓度范围在 1.3 至 17.2ng/ml 之间。重组 PGCP 具有酶活性，但没有 NAAG 水解活性。
GCPII 存在于人体血液中，其在健康人群中的浓度存在差异。重组 PGCP 不能水解 NAAG，表明在人血液中观察到的 NAAG 水解活性仅由 GCPII 单独负责。GCPII 血清水平与前列腺癌患者疾病状态之间的潜在相关性将进一步研究。
