Soni T, Brivet M, Moatti N, Dahan N, Lemonnier A
Laboratoire de Biochimie, Hôpital Bicêtre, Paris, France.
Clin Chim Acta. 1988 May 13;174(1):101-10. doi: 10.1016/0009-8981(88)90370-1.
Probands with the Philadelphia variant of galactokinase (GALKP) are black people who exhibit reduced galactokinase (GALK) activity in their red blood cells (RBC), but normal activity in their white blood cells (WBC). This reduced RBC GALK was demonstrated in disrupted erythrocytes. To investigate the possibility of a missing cofactor in hemolysates from individuals with GALKP phenotype, we compared [1-14C]galactose oxidation by intact erythrocytes, with the direct GALK assay in disrupted erythrocytes. The rate of [1-14C]glucose oxidation was also measured in order to differentiate an impaired galactose metabolism from a defect further along the pentose phosphate pathway. A good correlation (p less than 0.001) was found between the direct GALK assay and [1-14C]galactose oxidation in control subjects, which indicates that this method can be used effectively for the detection of GALK defects. This was further supported by studies on samples from heterozygotes and homozygotes for the GALKG deficient gene. For all the probands with a GALKP phenotype, diminished CO2 production from galactose was observed in the absence of impaired glucose metabolism. This allowed us to confirm the existence of a GALK deficiency in intact erythrocytes due to the GALKP variant. Further studies of RBC GALK catalytic properties are needed to investigate the molecular basis of this GALK deficiency.
患有费城型半乳糖激酶（GALKP）的先证者为黑人，他们的红细胞（RBC）中半乳糖激酶（GALK）活性降低，但白细胞（WBC）中的活性正常。这种红细胞GALK活性降低在破碎的红细胞中得到证实。为了研究GALKP表型个体的溶血产物中是否存在缺失的辅因子，我们将完整红细胞的[1-14C]半乳糖氧化与破碎红细胞中的直接GALK测定进行了比较。还测量了[1-14C]葡萄糖氧化速率，以区分半乳糖代谢受损与磷酸戊糖途径下游的缺陷。在对照受试者中，直接GALK测定与[1-14C]半乳糖氧化之间发现了良好的相关性（p小于0.001），这表明该方法可有效地用于检测GALK缺陷。对GALKG缺陷基因杂合子和纯合子样本的研究进一步支持了这一点。对于所有具有GALKP表型的先证者，在葡萄糖代谢未受损的情况下，观察到半乳糖产生的CO2减少。这使我们能够确认由于GALKP变异导致完整红细胞中存在GALK缺陷。需要进一步研究红细胞GALK的催化特性，以探讨这种GALK缺陷的分子基础。
