Bonney R J, Weinfeld H
J Bacteriol. 1971 Jun;106(3):812-8. doi: 10.1128/jb.106.3.812-818.1971.
A study was made of the regulation of three enzymes that act sequentially in the metabolism of thymidine in Escherichia coli K-12. Under a variety of conditions, two of the enzymes, thymidine phosphorylase and deoxyribose-5-phosphate aldolase, were found to be synthesized coordinately. However, the third enzyme, phosphodeoxyribomutase, was synthesized noncoordinately with the other two enzymes under the same conditions. In addition, the mutase could be fully induced, whereas basal levels of the phosphorylase and the aldolase were maintained. These findings indicate that two operons comprise the genes concerned with the reversible pathway leading from thymidine to acetaldehyde and glyceraldehyde-3-phosphate. In addition to thymidine, it was found that acetaldehyde was an external inducer of these enzymes. The results of induction experiments performed on wild-type cells and mutants defective in the mutase or the aldolase, with thymidine or acetaldehyde as exogenous inducers, strongly suggest that deoxyribose-5-phosphate is more proximal to the intracellular inducer than is thymidine, deoxyribose-1-phosphate, or acetaldehyde.
对大肠杆菌K - 12中胸苷代谢过程中依次起作用的三种酶的调节进行了研究。在各种条件下，发现其中两种酶，即胸苷磷酸化酶和脱氧核糖 - 5 - 磷酸醛缩酶是协同合成的。然而，第三种酶磷酸脱氧核糖变位酶在相同条件下与其他两种酶的合成不协同。此外，变位酶可以被完全诱导，而磷酸化酶和醛缩酶则维持基础水平。这些发现表明，两个操纵子包含了与从胸苷到乙醛和3 - 磷酸甘油醛的可逆途径相关的基因。除了胸苷外，还发现乙醛是这些酶的外部诱导剂。以胸苷或乙醛作为外源诱导剂，对野生型细胞以及变位酶或醛缩酶缺陷型突变体进行诱导实验的结果强烈表明，脱氧核糖 - 5 - 磷酸比胸苷、脱氧核糖 - 1 - 磷酸或乙醛更接近细胞内诱导剂。
