Noronha J M, Sheys G H, Buchanan J M
Proc Natl Acad Sci U S A. 1972 Aug;69(8):2006-10. doi: 10.1073/pnas.69.8.2006.
Cell-free extracts of Arbacia eggs (Arbacia punctulata) apparently do not contain an enzymatic system for the reduction of ribonucleotides to deoxyribonucleotides. However, during an interval of 5 hr after fertilization at 23 degrees , an enzymatic system is produced that is capable of catalyzing the reduction of CDP to dCDP in the presence of Mg(2+), ethylenediaminetetraacetate, ATP, and a reducing agent, dithiothreitol. The activity is first seen about 1 hr after fertilization, and reaches a peak at about 5 hr. The appearance of the ribonucleotide reductase is prevented by the addition of emetine or puromycin, inhibitors of protein synthesis, to the cells before fertilization. Inclusion of actinomycin D in the cell suspension at a concentration sufficient to inhibit synthesis of messenger RNA does not appreciably affect the production of the enzyme activity. Preexisting, maternal RNA is thus used for synthesis of reductase. Ribonucleotide reductase may, therefore, represent the first example of an enzyme system absent in unfertilized eggs that is produced in response to fertilization.
海胆卵（刺冠海胆）的无细胞提取物显然不含有将核糖核苷酸还原为脱氧核糖核苷酸的酶系统。然而，在23摄氏度受精后的5小时内，会产生一种酶系统，该系统在镁离子（Mg²⁺）、乙二胺四乙酸、三磷酸腺苷（ATP）和还原剂二硫苏糖醇存在的情况下，能够催化胞苷二磷酸（CDP）还原为脱氧胞苷二磷酸（dCDP）。这种活性在受精后约1小时首次出现，并在约5小时达到峰值。在受精前向细胞中添加放线菌酮或嘌呤霉素（蛋白质合成抑制剂）可阻止核糖核苷酸还原酶的出现。以足以抑制信使核糖核酸（mRNA）合成的浓度将放线菌素D加入细胞悬液中，并不会明显影响酶活性的产生。因此，预先存在的母体RNA被用于还原酶的合成。核糖核苷酸还原酶可能是未受精卵中不存在但在受精后产生的酶系统的首个例子。
