Leito Jorge H, S-Correia Isabel
Laboratrio de Engenharia Bioqumica, Centro de Engenharia Biolgica e Qumica, Instituto Superior Tcnico, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal.
Microbiology (Reading). 1997 Feb;143(2):481-488. doi: 10.1099/00221287-143-2-481.
Alginate production and degree of polymerization were affected when the highly mucoid 8821M was grown with growth-inhibitory concentrations of Cu (supplied as CuCl; 1-5 mM). The inhibition of alginate biosynthesis was consistent with the decreased activity in Cu-stressed cells of phosphomannose isomerase/GDP-mannose pyrophosphorylase (encoded by ), phosphomannomutase (encoded by ) and GDP-mannose dehydrogenase (encoded by ). However, in cells grown with concentrations of CuCl below 2 mM, the steady-state mRNA levels from and from the regulatory gene increased moderately. This observation is consistent with the suggested linkage between the control of alginate gene expression and the global regulation involved in the oxidative stress response. At highly inhibitory concentrations the levels of the four alginate gene transcripts decreased from maximal values. The bell-shaped curves, representing the effect of Cu concentration on mRNA levels from the four alginate genes, exhibited similar patterns but did not concur. The decrease of the specific activity of enzymes necessary for GDP-mannuronic acid synthesis in Cu-grown cells was correlated with changes in gene expression, with the inhibitory effect of Cu on enzyme activities and with Cu-induced oxidative inactivation of enzymes, especially the particularly sensitive phosphomannose isomerase activity.
当高黏液性的8821M在含有生长抑制浓度铜（以CuCl形式提供；1 - 5 mM）的培养基中生长时，藻酸盐的产生和聚合度受到影响。藻酸盐生物合成的抑制与铜胁迫细胞中磷酸甘露糖异构酶/GDP - 甘露糖焦磷酸化酶（由 编码）、磷酸甘露糖变位酶（由 编码）和GDP - 甘露糖脱氢酶（由 编码）活性的降低相一致。然而，在含有低于2 mM CuCl的培养基中生长的细胞中， 和调控基因 的稳态mRNA水平适度增加。这一观察结果与藻酸盐基因表达调控与氧化应激反应中涉及的全局调控之间的推测联系相一致。在高抑制浓度下，四种藻酸盐基因转录本的水平从最大值下降。代表铜浓度对四种藻酸盐基因mRNA水平影响的钟形曲线呈现出相似的模式，但并不完全一致。在铜处理的细胞中，GDP - 甘露糖醛酸合成所需酶的比活性降低与基因表达的变化、铜对酶活性的抑制作用以及铜诱导的酶氧化失活相关，尤其是对特别敏感的磷酸甘露糖异构酶活性的影响。
