Snyder F F, Mendelsohn J, Seegmiller J E
J Clin Invest. 1976 Sep;58(3):654-66. doi: 10.1172/JCI108512.
The association of a human genetic deficiency of adenosine deaminase activity with combined immunodeficiency prompted a study of the effects of adenosine and of inhibition of adenosine deaminase activity on human lymphocyte transformation and a detailed study of adenosine metabolism throughout phytohemagglutinin-induced blastogenesis. The adenosine deaminase inhibitor, coformycin, at a concentration that inhibited adenosine deaminase activity more than 95%, or 50 muM adenosine, did not prevent blastogenesis by criteria of morphology or thymidine incorporation into acid-precipitable material. The combination of coformycin and adenosine, however, substantially reduced both the viable cell count and the incorporation of thymidine into DNA in phytohemagglutinin-stimulated lymphocytes. Incubation of lymphocytes with phytohemagglutinin for 72 h produced a 12-fold increase in the rate of deamination and a 6-fold increase in phosphorylation of adenosine by intact lymphocytes. There was no change in the apparent affinity for adenosine with either deamination or phosphorylation. The increased rates of metabolism, apparent as early as 3 h after addition of mitogen, may be due to increased entry of the nucleoside into stimulated lymphocytes. Increased adenosine metabolism was not due to changes in total enzyme activity; after 72 h in culture, the ratios of specific activities in extracts of stimulated to unstimulated lymphocytes were essentially unchanged for adenosine kinase, 0.92, and decreased for adenosine deaminase, 0.44. As much as 38% of the initial lymphocyte adenosine deaminase activity accumulated extracellularly after a 72-h culture with phytohemagglutinin. In phytohemagglutinin-stimulated lymphocytes, the principal route of adenosine metabolism was phosphorylation at less than 5 muM adenosine, and deamination at concentrations greater than 5 muM. In unstimulated lymphocytes, deamination was the principal route of adenosine metabolism over the range of adenosine concentrations studied (0.5-250 muM). These studies demonstrate the dependence of both the unstimulated and stimulated lymphocyte on adenosine and may account for the observed sensitivity of mitogen-stimulated lymphocytes to the toxic effects of exogenously supplied adenosine in the presence of the adenosine deaminase inhibitor coformycin. A single case of immunodeficiency disease has been reported in association with purine nucleoside phosphorylase deficiency. The catabolism of guanosine was also found to be enhanced in stimulated normal lymphocytes; phosphorolysis of guanosine to guanine by intact lymphocytes increased six fold after 72-h culture with phytohemagglutinin. The specific activity of purine nucleoside phosphorylase in extracts, with guanosine as substrate, was essentially the same in stimulated and unstimulated lymphocytes after 72 h of culture.
人类腺苷脱氨酶活性的遗传缺陷与联合免疫缺陷的关联促使人们研究腺苷以及腺苷脱氨酶活性抑制对人淋巴细胞转化的影响，并对植物血凝素诱导的细胞分裂增殖过程中的腺苷代谢进行详细研究。腺苷脱氨酶抑制剂助间霉素，在其浓度能抑制腺苷脱氨酶活性超过95%时，或50μM腺苷，依据形态学标准或胸苷掺入酸沉淀物质的情况，并未阻止细胞分裂增殖。然而，助间霉素与腺苷的组合，显著降低了植物血凝素刺激的淋巴细胞中的活细胞计数以及胸苷掺入DNA的情况。用植物血凝素孵育淋巴细胞72小时，完整淋巴细胞的腺苷脱氨速率增加了12倍，腺苷磷酸化增加了6倍。脱氨或磷酸化时对腺苷的表观亲和力没有变化。代谢速率的增加，早在添加促细胞分裂剂后3小时就明显可见，可能是由于核苷进入受刺激淋巴细胞的量增加。腺苷代谢增加并非由于总酶活性的变化；培养72小时后，受刺激淋巴细胞提取物与未受刺激淋巴细胞提取物的比活性，对于腺苷激酶基本不变，为0.92，对于腺苷脱氨酶则降低，为0.44。用植物血凝素培养72小时后，初始淋巴细胞腺苷脱氨酶活性多达38%在细胞外积累。在植物血凝素刺激的淋巴细胞中，当腺苷浓度低于5μM时，腺苷代谢的主要途径是磷酸化，当浓度高于5μM时则是脱氨。在未受刺激的淋巴细胞中，在所研究的腺苷浓度范围（0.5 - 250μM）内，脱氨是腺苷代谢的主要途径。这些研究证明了未受刺激和受刺激的淋巴细胞对腺苷的依赖性，并且可能解释了在腺苷脱氨酶抑制剂助间霉素存在的情况下，观察到的促细胞分裂剂刺激的淋巴细胞对外源性供应的腺苷毒性作用的敏感性。已经报道了一例与嘌呤核苷磷酸化酶缺乏相关的免疫缺陷疾病病例。还发现受刺激的正常淋巴细胞中鸟苷的分解代谢也增强；用植物血凝素培养72小时后，完整淋巴细胞将鸟苷磷酸解为鸟嘌呤的过程增加了6倍。培养72小时后，以鸟苷为底物时，受刺激和未受刺激淋巴细胞提取物中嘌呤核苷磷酸化酶的比活性基本相同。
