Beckage M J, Blumenstein M, Kisliuk R L
Biochim Biophys Acta. 1979 Nov 9;571(1):157-61. doi: 10.1016/0005-2744(79)90236-5.
The 31P nuclear magnetic resonance signal of deoxyuridylate was studied in the presence and absence of thymidlate synthase. In the absence of enzyme the chemical shift of deoxyuridylate is pH dependent with a pKa of 6.25. In the presence of enzyme, a peak corresponding to the dianioinc form of deoxyuridylate is observed which is independent of pH between pH 5.7 and pH 7.4. The pKa of the phosphate in the deoxyuridylate-thymidylate synthase complex is therefore less than 5. The release of inorganic phosphate from deoxyuridylate catalyzed by contaminating phosphatase was also observed.
在有和没有胸苷酸合成酶的情况下，对脱氧尿苷酸的31P核磁共振信号进行了研究。在没有酶的情况下，脱氧尿苷酸的化学位移取决于pH值，其pKa为6.25。在有酶的情况下，观察到一个与脱氧尿苷酸二价阴离子形式相对应的峰，该峰在pH 5.7至pH 7.4之间与pH无关。因此，脱氧尿苷酸 - 胸苷酸合成酶复合物中磷酸盐的pKa小于5。还观察到了由污染的磷酸酶催化的脱氧尿苷酸释放无机磷酸盐的情况。
