Farfán M J, Martín-Rendón E, Calderón I L
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Ap. 1095, E-41080 Sevilla, Spain.
Biotechnol Bioeng. 1996 Mar 20;49(6):667-74. doi: 10.1002/(SICI)1097-0290(19960320)49:6<667::AID-BIT8>3.0.CO;2-M.
In this work, we have studied the effect of amplifying different alleles involved in the threonine biosynthesis on the amino acid production by Saccharomyces cerevisiae. The genes used were wild-type HOM3, HOM2, HOM6, THR1, and THR4, and two mutant alleles of HOM3 (namely HOM3-R2 and HOM3-R6), that code for feedback-insensitive aspartate kinases. The results show that only the amplification of the HOM3 alleles leads to threonine and, in some instances, to homoserine overproduction. In terms of the regulation of the pathway, the data indicate that the main control is exerted by inhibition of the aspartate kinase and that, probably, a second and less important regulation takes place at the level of the homoserine kinase, the THR1 gene product. However, amplification of THR1 in two related Hom3-R2 strains does not increase the amount of threonine but, in one of them, it does induce accumulation of more homoserine. This result probably reflects differences between these strains in some undetermined genetic factor/s related with threonine metabolism. In general, the data indicate that the common laboratory yeast strains are genetically rather heterogeneous and, thus, extrapolation of conclusions must be done carefully. (c) 1996 John Wiley & Sons, Inc.
在这项研究中，我们研究了扩增参与苏氨酸生物合成的不同等位基因对酿酒酵母氨基酸产量的影响。所使用的基因有野生型HOM3、HOM2、HOM6、THR1和THR4，以及HOM3的两个突变等位基因（即HOM3-R2和HOM3-R6），它们编码对反馈不敏感的天冬氨酸激酶。结果表明，只有HOM3等位基因的扩增会导致苏氨酸过量生产，在某些情况下还会导致高丝氨酸过量生产。就该途径的调控而言，数据表明主要调控是通过抑制天冬氨酸激酶实现的，并且可能在高丝氨酸激酶（THR1基因产物）水平发生次要且不太重要的调控。然而，在两个相关的Hom3-R2菌株中扩增THR1并不会增加苏氨酸的产量，但在其中一个菌株中，它确实会诱导更多高丝氨酸的积累。这一结果可能反映了这些菌株在与苏氨酸代谢相关的一些未确定的遗传因素上的差异。总体而言，数据表明常见的实验室酵母菌株在遗传上相当异质，因此，结论的外推必须谨慎进行。(c) 1996 John Wiley & Sons, Inc.
