BOTH MUTATIONS IN G6PD-A- ARE NECESSARY TO PRODUCE THE G6PD DEFICIENT PHENOTYPE
BOTH MUTATIONS IN G6PD-A- ARE NECESSARY TO PRODUCE THE G6PD DEFICIENT PHENOTYPE
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DOI：
10.1093/hmg/1.3.171
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发表时间：
1992-06-01
影响因子：
3.5
通讯作者：
LUZZATTO, L
中科院分区：
文献类型：
--
作者：
TOWN, M;BAUTISTA, JM;LUZZATTO, L
葡萄糖6-磷酸脱氢酶(G6PD)缺乏症在非洲人群中的高度流行几乎完全是由于酶变体A-，它与野生型G6PD B不同，有两个氨基酸替换，68Val--&Gt；Met和126 Asn--&Gt；Asp。无缺陷的多态突变体G6PD A仅包含突变126 Asn--&Gt；Asp。在非洲部分地区，G6PD A和G6PD A基因的频率都在0.2左右。在B背景中未发现68Val--&Gt；Met突变。这可能是因为68Val--&Gt；Met突变最初碰巧出现在A基因中，或者因为68Val--&Gt；Met突变本身不足以导致G6PD缺乏症。我们通过在细菌表达系统中生产G6PD B，A，A-和G6PD 68 Val--&Gt；Met并分析它们的生化性质来解决这个问题。对于每个单独的突变，我们发现与G6PD B相比，酶的比活力和产量都略有下降。当两个突变一起引入时，对比活力有大致的相加效应，但对酶产量的影响要大得多(正常的4%)。这种协同效应在热稳定性方面也得到了证实，尤其是在低浓度的NADP下。当研究119Gln-->；Glu替代126Asn-->；Asp时，产生了可比较的结果。我们推测，这两个突变的共存是G6PD A-酶缺乏的原因，因为它们在导致酶的不稳定方面起协同作用。
The high prevalence of glucose 6-phosphate dehydrogenase (G6PD) deficiency in African populations is due almost entirely to the enzyme variant A-, which differs from the wild-type G6PD B by two amino acid replacements, 68 Val-->Met and 126 Asn-->Asp. The non-deficient polymorphic variant G6PD A contains only the mutation 126 Asn-->Asp. The frequencies of the G6PD A and of the G6PD A- genes in parts of Africa are both about 0.2. The 68 Val-->Met mutation has not been found in a B background. This could be because the 68 Val-->Met mutation happened to arise in an A gene in the first instance, or because the 68 Val-->Met mutation alone is not sufficient to cause G6PD deficiency. We have approached this question by producing G6PD B, A, A-, and G6PD 68 Val-->Met in a bacterial expression system and analysing their biochemical properties. With each single mutation we found a slight decrease in both the specific activity and the yield of enzyme when compared to G6PD B. When both mutations were introduced together, there was a roughly additive effect on specific activity, but a much more drastic effect on enzyme yield (4% of normal). This synergistic effect was also demonstrated on thermal stability, especially at low NADP concentrations. Comparable results were produced when the replacement 119 Gln-->Glu was studied instead of 126 Asn-->Asp. We infer that the coexistence of the two mutations is responsible for enzyme deficiency in G6PD A- because they act synergistically in causing instability of the enzyme.