Brosh S, Boer P, Kupfer B, de Vries A, Sperling O
J Clin Invest. 1976 Aug;58(2):289-97. doi: 10.1172/JCI108471.
Human peripheral blood leukocytes were studied for the presence and the regulatory properties of the pathway of de novo synthesis of purine nucleotides. The cells were found to incorporate the labeled precursors formate and glycine into purines. The rate of [14C]-formate incorporation was decreased by several compounds known to inhibit purine synthesis by affecting the activity by glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase, the first committed enzyme in the pathway, either through decreasing the availability of PRPP, a substrate for this enzyme, or through exerting inhibition on this enzyme. PRPP availability in the leukocyte was found to be limiting for purine synthesis. Increased PRPP availability resulting from activation of PRPP synthetase by increasing inorganic phosphate (Pi) concentration caused acceleration of purine synthesis. On the other hand, no clear-cut evidence was obtained for the availability of ribose-5-phosphate in the leukocyte being rate limiting at physiological extracellular Pi concentration for PRPP generation, and thus for purine synthesis. However, the addition of methylene blue, which accelerates the oxidative pentose shunt that produces ribose-5-phosphate, resulted in acceleration of PRPP generation and of purine synthesis only when PRPP synthetase was largely activated at high Pi concentration. These results may be taken to suggest that ribose-5-phosphate availability is indeed not limiting for PRPP generation under physiological conditions. Purine synthesis de novo was accelerated more than 13-fold in the leukocytes of two gouty patients affected with partial deficiency of hypoxanthine-guanine phosphoribosyltransferase, but was normal in the leukocytes of an obligate heterozygote for this enzyme abnormality. The results domonstrate in peripheral human leukocytes the presence of the complete pathway of de novo synthesis of purine nucleotides and the manifestation in these cells of the biochemical consequences of hypoxanthine-guanine phosphoribosyltransferase deficiency, i.e., increased availability of PRPP and acceleration of purine synthesis de novo. The results indicate the usefulness of leukocytes as a model tissue for the study of purine metabolism in man.
对人外周血白细胞中嘌呤核苷酸从头合成途径的存在情况及其调节特性进行了研究。发现这些细胞能将标记的前体甲酸和甘氨酸掺入嘌呤中。[14C] - 甲酸掺入率因几种已知通过影响谷氨酰胺磷酸核糖焦磷酸（PRPP）酰胺转移酶活性来抑制嘌呤合成的化合物而降低，该酶是该途径中的第一个关键酶，这些化合物要么通过降低该酶的底物PRPP的可用性，要么通过对该酶施加抑制作用来实现。发现白细胞中PRPP的可用性对嘌呤合成具有限制作用。通过增加无机磷酸盐（Pi）浓度激活PRPP合成酶导致PRPP可用性增加，从而加速了嘌呤合成。另一方面，在生理细胞外Pi浓度下，没有获得明确证据表明白细胞中5 - 磷酸核糖的可用性是PRPP生成以及嘌呤合成的限速因素。然而，添加亚甲蓝可加速产生5 - 磷酸核糖的氧化戊糖支路，仅当PRPP合成酶在高Pi浓度下被大量激活时，才会导致PRPP生成加速和嘌呤合成加速。这些结果可能表明在生理条件下5 - 磷酸核糖的可用性确实不是PRPP生成的限制因素。两名患有次黄嘌呤 - 鸟嘌呤磷酸核糖转移酶部分缺乏症的痛风患者的白细胞中，嘌呤从头合成加速了13倍以上，但该酶异常的 obligate杂合子的白细胞中嘌呤合成正常。这些结果证明了人外周血白细胞中存在嘌呤核苷酸从头合成的完整途径，以及次黄嘌呤 - 鸟嘌呤磷酸核糖转移酶缺乏的生化后果在这些细胞中的表现，即PRPP可用性增加和嘌呤从头合成加速。这些结果表明白细胞作为研究人类嘌呤代谢的模型组织是有用的。
