Nasser D, Henderson G, Nester E W
J Bacteriol. 1969 Apr;98(1):44-50. doi: 10.1128/jb.98.1.44-50.1969.
Several regulated enzymes involved in aromatic amino acid synthesis were studied in Bacillus subtilis and B. licheniformis with reference to organization and control mechanisms. B. subtilis has been previously shown (23) to have a single 3-deoxy-d-arabinoheptulosonate 7-phosphate (DAHP) synthetase but to have two isozymic forms of both chorismate mutase and shikimate kinase. Extracts of B. licheniformis chromatographed on diethylaminoethyl (DEAE) cellulose indicated a single DAHP synthetase and two isozymic forms of chorismate mutase, but only a single shikimate kinase activity. The evidence for isozymes has been supported by the inability to find strains mutant in these activities, although strains mutant for the other activities were readily obtained. DAHP synthetase, one of the isozymes of chorismate mutase, and one of the isozymes of shikimate kinase were found in a single complex in B. subtilis. No such complex could be detected in B. licheniformis. DAHP synthetase and shikimate kinase from B. subtilis were feedback-inhibited by chorismate and prephenate. DAHP synthetase from B. licheniformis was also feedback-inhibited by these two intermediates, but shikimate kinase was inhibited only by chorismate. When the cells were grown in limiting tyrosine, the DAHP synthetase, chorismate mutase, and shikimate kinase activities of B. subtilis were derepressed in parallel, but only DAHP synthetase and chorismate mutase were derepressible in B. licheniformis. Implications of the differences as well as the similarities between the control and the pattern of enzyme aggregation in the two related species of bacilli were discussed.
针对组织和控制机制，对枯草芽孢杆菌和地衣芽孢杆菌中几种参与芳香族氨基酸合成的调控酶进行了研究。先前已表明（23），枯草芽孢杆菌具有单一的3-脱氧-d-阿拉伯庚酮糖酸7-磷酸（DAHP）合成酶，但分支酸变位酶和莽草酸激酶均有两种同工酶形式。在地衣芽孢杆菌提取物在二乙氨基乙基（DEAE）纤维素上进行色谱分析，结果显示有单一的DAHP合成酶和两种分支酸变位酶同工酶形式，但只有单一的莽草酸激酶活性。尽管很容易获得其他活性的突变菌株，但未能找到这些活性的突变菌株，这支持了同工酶的存在。在枯草芽孢杆菌中，DAHP合成酶、一种分支酸变位酶同工酶和一种莽草酸激酶同工酶存在于一个单一的复合物中。在地衣芽孢杆菌中未检测到这样的复合物。枯草芽孢杆菌的DAHP合成酶和莽草酸激酶受到分支酸和预苯酸的反馈抑制。地衣芽孢杆菌的DAHP合成酶也受到这两种中间产物的反馈抑制，但莽草酸激酶仅受到分支酸的抑制。当细胞在酪氨酸受限的条件下生长时，枯草芽孢杆菌的DAHP合成酶、分支酸变位酶和莽草酸激酶活性同时被去阻遏，但在地衣芽孢杆菌中只有DAHP合成酶和分支酸变位酶可被去阻遏。讨论了这两种相关芽孢杆菌在酶聚集的控制和模式方面的差异及相似性的意义。
