Kicska G A, Long L, Hörig H, Fairchild C, Tyler P C, Furneaux R H, Schramm V L, Kaufman H L
Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Proc Natl Acad Sci U S A. 2001 Apr 10;98(8):4593-8. doi: 10.1073/pnas.071050798. Epub 2001 Apr 3.
Transition-state theory has led to the design of Immucillin-H (Imm-H), a picomolar inhibitor of purine nucleoside phosphorylase (PNP). In humans, PNP is the only route for degradation of deoxyguanosine, and genetic deficiency of this enzyme leads to profound T cell-mediated immunosuppression. This study reports the biological effects and mechanism of action of Imm-H on malignant T cell lines and on normal activated human peripheral T cells. Imm-H inhibits the growth of malignant T cell leukemia lines with the induction of apoptosis. Imm-H also inhibits activated normal human T cells after antigenic stimulation in vitro. However, Imm-H did not inhibit malignant B cells, colon cancer cell lines, or normal human nonstimulated T cells, demonstrating the selective activity of Imm-H. The effects on leukemia cells were mediated by the cellular phosphorylation of deoxyguanosine and the accumulation of dGTP, an inhibitor of ribonucleotide diphosphate reductase. Cells were protected from the toxic effects of Imm-H when deoxyguanosine was absent or when deoxycytidine was present. Guanosine incorporation into nucleic acids was selectively blocked by Imm-H with no effect on guanine, adenine, adenosine, or deoxycytidine incorporation. Imm-H may have clinical potential for treatment of human T cell leukemia and lymphoma and for other diseases characterized by abnormal activation of T lymphocytes. The design of Imm-H from an enzymatic transition-state analysis exemplifies a powerful approach for developing high-affinity enzyme inhibitors with pharmacologic activity.
过渡态理论促成了免疫胞苷-H（Imm-H）的设计，它是嘌呤核苷磷酸化酶（PNP）的一种皮摩尔级抑制剂。在人类中，PNP是脱氧鸟苷降解的唯一途径，该酶的基因缺陷会导致严重的T细胞介导的免疫抑制。本研究报告了Imm-H对恶性T细胞系和正常活化的人外周T细胞的生物学效应及作用机制。Imm-H通过诱导凋亡抑制恶性T细胞白血病系的生长。Imm-H还能在体外抑制抗原刺激后活化的正常人T细胞。然而，Imm-H不抑制恶性B细胞、结肠癌细胞系或正常未受刺激的人T细胞，表明了Imm-H的选择性活性。对白血病细胞的作用是由脱氧鸟苷的细胞磷酸化和核糖核苷酸二磷酸还原酶的抑制剂dGTP的积累介导的。当不存在脱氧鸟苷或存在脱氧胞苷时，细胞可免受Imm-H的毒性作用。Imm-H选择性地阻断鸟苷掺入核酸，而对鸟嘌呤、腺嘌呤、腺苷或脱氧胞苷的掺入没有影响。Imm-H在治疗人类T细胞白血病和淋巴瘤以及其他以T淋巴细胞异常活化特征的疾病方面可能具有临床潜力。基于酶促过渡态分析设计Imm-H例证了一种开发具有药理活性的高亲和力酶抑制剂的有效方法。
