Casellas M, Grifoll M, Bayona J M, Solanas A M
Departament of Microbiologia, Universitat de Barcelona, Spain.
Appl Environ Microbiol. 1997 Mar;63(3):819-26. doi: 10.1128/aem.63.3.819-826.1997.
Identification of new metabolites and demonstration of key enzyme activities support and extend the pathways previously reported for fluorene metabolism by Arthrobacter sp. strain F101. Washed-cell suspensions of strain F101 with fluorene accumulated 9-fluorenone, 4-hydroxy-9-fluorenone, 3-hydroxy-1-indanone, 1-indanone, 2-indanone, 3-(2-hydroxyphenyl) propionate, and a compound tentatively identified as a formyl indanone. Incubations with 2-indanone produced 3-isochromanone. The growth yield with fluorene as a sole source of carbon and energy corresponded to an assimilation of about 34% of fluorene carbon. About 7.4% was transformed into 9-fluorenol, 9-fluorenone, and 4-hydroxy-9-fluorenone. Crude extracts from fluorene-induced cells showed 3,4-dihydrocoumarin hydrolase and catechol 2,3-dioxygenase activities. These results and biodegradation experiments with the identified metabolites indicate that metabolism of fluorene by Arthrobacter sp. strain F101 proceeds through three independent pathways. Two productive routes are initiated by dioxygenation at positions 1,2 and 3,4, respectively. meta cleavage followed by an aldolase reaction and loss of C-1 yield the detected indanones. Subsequent biological Baeyer-Villiger reactions produce the aromatic lactones 3,4-dihydrocoumarin and 3-isochromanone. Enzymatic hydrolysis of the former gives 3-(2-hydroxyphenyl) propionate, which could be a substrate for a beta oxidation cycle, to give salicylate. Further oxidation of the latter via catechol and 2-hydroxymuconic semialdehyde connects with the central metabolism, allowing the utilization of all fluorene carbons. Identification of 4-hydroxy-9-fluorenone is consistent with an alternative pathway initiated by monooxygenation at C-9 to give 9-fluorenol and then 9-fluorenone. Although dioxygenation at 3,4 positions of the ketone apparently occurs, this reaction fails to furnish a subsequent productive oxidation of this compound.
新代谢产物的鉴定以及关键酶活性的证明支持并拓展了先前报道的节杆菌属菌株F101芴代谢途径。用芴处理的F101菌株洗涤细胞悬液积累了9-芴酮、4-羟基-9-芴酮、3-羟基-1-茚酮、1-茚酮、2-茚酮、3-(2-羟基苯基)丙酸酯以及一种暂定为甲酰茚酮的化合物。用2-茚酮孵育产生了3-异苯并二氢吡喃酮。以芴作为唯一碳源和能源时的生长产量相当于约34%的芴碳被同化。约7.4%转化为9-芴醇、9-芴酮和4-羟基-9-芴酮。芴诱导细胞的粗提物显示出3,4-二氢香豆素水解酶和儿茶酚2,3-双加氧酶活性。这些结果以及对已鉴定代谢产物的生物降解实验表明，节杆菌属菌株F101对芴的代谢通过三条独立途径进行。两条有效途径分别由在第1、2位和第3、4位的双加氧反应启动。间位裂解随后进行醛缩酶反应并失去C-1产生检测到的茚酮。随后的生物拜耳-维利格反应产生芳香内酯3,4-二氢香豆素和3-异苯并二氢吡喃酮。前者的酶促水解产生3-(2-羟基苯基)丙酸酯，它可能是β氧化循环的底物，生成水杨酸酯。后者通过儿茶酚和2-羟基粘康酸半醛的进一步氧化与中心代谢相连，从而使所有芴碳得以利用。4-羟基-9-芴酮的鉴定与由C-9位单加氧反应生成9-芴醇然后生成9-芴酮的替代途径一致。尽管酮的3,4位显然发生了双加氧反应，但该反应未能为该化合物提供后续的有效氧化。
