Wild J, Zakrzewska B, Walczak W, Kłopotowski T
Acta Microbiol Pol. 1987;36(1-2):17-28.
We showed that the ability of Escherichia coli K12 tryptophan auxotrophs to utilize D-tryptophan as a substitute for L-tryptophan may result from two types of mutations. The first type consisted in changes in the dadR regulatory site of the dad operon increasing the synthesis of D-amino acid dehydrogenase. The mutations of the second type mapped within the dad A structural gene. They changed the apparent substrate specificity of D-amino acid dehydrogenase. We suppose that the change may be due to an altered enzyme structure which make it more accessible to D-tryptophan.
我们发现，大肠杆菌K12色氨酸营养缺陷型利用D-色氨酸替代L-色氨酸的能力可能源于两种类型的突变。第一种类型是dad操纵子的dadR调控位点发生变化，增加了D-氨基酸脱氢酶的合成。第二种类型的突变位于dadA结构基因内。它们改变了D-氨基酸脱氢酶的表观底物特异性。我们推测，这种变化可能是由于酶结构的改变，使其更容易接近D-色氨酸。
