Condemine G, Hugouvieux-Cotte-Pattat N, Robert-Baudouy J
J Bacteriol. 1986 Mar;165(3):937-41. doi: 10.1128/jb.165.3.937-941.1986.
Mutants of Erwinia chrysanthemi impaired in pectin degradation were isolated by chemical and Mu d(Ap lac) insertion mutagenesis. A mutation in the kduD gene coding for 2-keto-3-deoxygluconate oxidoreductase prevented the growth of the bacteria on polygalacturonate as the sole carbon source. Analysis of the kduD::Mu d(Ap lac) insertions indicated that kduD is either an isolated gene or the last gene of a polycistronic operon. Some of the Mu d(Ap lac) insertions were kduD-lac fusions in which beta-galactosidase synthesis reflected kduD gene expression. In all these fusions, beta-galactosidase activity was shown to be sensitive to catabolite repression by glucose and to be inducible by polygalacturonate, galacturonate, and other intermediates of polygalacturonate catabolism. Galacturonate-mediated induction was prevented by a mutation which blocked its metabolism to 2-keto-3-deoxygluconate. 2-Keto-3-deoxygluconate appeared to be the true inducer of kduD expression resulting from galacturonate degradation. 5-Keto-4-deoxyuronate or 2,5-diketo-3-deoxygluconate were the true inducers, originating from polygalacturonate cleavage. These three intermediates also appeared to induce pectate lyases, oligogalacturonate lyase, and 5-keto-4-deoxyuronate isomerase synthesis.
通过化学诱变和 Mud(Ap lac)插入诱变，分离得到了在果胶降解方面有缺陷的菊欧文氏菌突变体。编码 2-酮-3-脱氧葡糖酸氧化还原酶的 kduD 基因发生突变，阻止了细菌以聚半乳糖醛酸作为唯一碳源生长。对 kduD::Mud(Ap lac)插入片段的分析表明，kduD 要么是一个孤立基因，要么是一个多顺反子操纵子的最后一个基因。一些 Mud(Ap lac)插入片段是 kduD-lac 融合体，其中β-半乳糖苷酶的合成反映了 kduD 基因的表达。在所有这些融合体中，β-半乳糖苷酶活性显示对葡萄糖的分解代谢物阻遏敏感，并且可被聚半乳糖醛酸、半乳糖醛酸和聚半乳糖醛酸分解代谢的其他中间产物诱导。半乳糖醛酸介导的诱导被一个阻止其代谢为 2-酮-3-脱氧葡糖酸的突变所阻断。2-酮-3-脱氧葡糖酸似乎是半乳糖醛酸降解导致的 kduD 表达的真正诱导物。5-酮-4-脱氧uronate 或 2,5-二酮-3-脱氧葡糖酸是真正的诱导物，源自聚半乳糖醛酸的裂解。这三种中间产物似乎也诱导果胶酸裂解酶、寡聚半乳糖醛酸裂解酶和 5-酮-4-脱氧uronate 异构酶的合成。
