The savory or umami taste of the amino acid glutamate is synergistically enhanced by the addition of the purines inosine 5’-monophosphate (IMP) and guanosine 5’-monophosphate (GMP) disodium salt. We hypothesized that the addition of purinergic ribonucleotides, along with the pyrimidine ribonucleotides, would decrease the absolute detection threshold of (increase sensitivity to) L-glutamic acid potassium salt (MPG). To test this, we measured both the absolute detection threshold of MPG alone and with a background level (3 mM) of five different 5’-ribonucleotides. The addition of the three purines IMP, GMP, and adenosine 5’-monophosphate (AMP) lowered the MPG threshold in all participants (p <0.001), indicating they are positive modulators or enhancers of glutamate taste. The average detection threshold of MPG was 2.08 mM and with the addition of IMP the threshold was decreased by approximately 1.5 orders of magnitude to 0.046 mM. In contrast to the purines, the pyrimidines uridine 5’-monophosphate (UMP) and cytidine 5’-monophosphate (CMP) yielded different results. CMP reliably raised glutamate thresholds in 10 of 17 subjects, suggesting it is a negative modulator or diminisher of glutamate taste for them. The rank order of effects on increasing sensitivity to glutamate was IMP > GMP> AMP >> UMP // CMP. These data confirm that ribonucleotides are modulators of glutamate taste, with purines enhancing sensitivity and pyrimidines displaying variable and even negative modulatory effects. Our ability to detect the co-occurrence of glutamate and purines is meaningful as both are relatively high in evolutionarily important sources of nutrition, such as insects and fermented foods.

中文翻译：

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核糖核苷酸差异调节口腔谷氨酸检测阈值

通过添加嘌呤肌苷 5'-单磷酸 (IMP) 和鸟苷 5'-单磷酸 (GMP) 二钠盐，可协同增强氨基酸谷氨酸的咸味或鲜味。我们假设添加嘌呤核糖核苷酸以及嘧啶核糖核苷酸会降低 L-谷氨酸钾盐 (MPG) 的绝对检测阈值（增加灵敏度）。为了测试这一点，我们单独测量了 MPG 的绝对检测阈值，并测量了五种不同 5'-核糖核苷酸的背景水平 (3 mM)。添加三种嘌呤 IMP、GMP 和 5'-单磷酸腺苷 (AMP) 降低了所有参与者的 MPG 阈值 (p <0.001)，表明它们是谷氨酸味觉的正调节剂或增强剂。MPG 的平均检测阈值为 2.08 mM，添加 IMP 后，阈值降低约 1.5 个数量级，达到 0.046 mM。与嘌呤相反，嘧啶尿苷5'-单磷酸（UMP）和胞苷5'-单磷酸（CMP）产生了不同的结果。CMP 确实提高了 17 名受试者中 10 名的谷氨酸阈值，这表明它对他们来说是谷氨酸味觉的负调节剂或减弱剂。对谷氨酸敏感性增加的效果的排序是IMP＞1。GMP> AMP>> UMP // CMP。这些数据证实核糖核苷酸是谷氨酸味道的调节剂，嘌呤增强敏感性，而嘧啶显示可变甚至负调节作用。我们检测谷氨酸和嘌呤共存的能力是有意义的，因为两者在进化上重要的营养来源中含量相对较高，例如昆虫和发酵食品。