SUMMARY: sp. (strain C1) was isolated by elective culture with 1,8-cineole as sole carbon source. 6--Hydroxycineole and 6-oxocineole accumulated transiently during the latter part of the exponential growth phase and, together with 1,8-cineole, were oxidized rapidly by 1,8-cineole-grown cells. Although a putative 1,8-cineole monooxygenase was not detected in cell-free systems an induced 6--hydroxycineole dehydrogenase and an induced NADPH-linked 6-oxocineole oxygenase were readily demonstrated. The lactone 5,5-dimethyl-4-(3′-oxobutyl)-4,5-dihydrofuran-2(3H)-one was isolated from oxygenation reactions with 6-oxocineole as substrate. This was not the immediate product of oxygenation but resulted from non-enzymic lactonization of the ring cleavage intermediate 3-(1-hydroxy-1-methylethyl)-6-oxoheptanoic acid during extraction procedures. 2,5-Diketocamphane 1,2-monooxygenase purified from (+)-camphor-grown ATCC 17453 was also able to utilize 6-oxocineole as a substrate with formation of the same isolated product. The established oxygen-insertion specificity of this enzyme coupled with an unequivocal absence of esterase activity allowed the nature of the oxygen insertion into 6-oxocineole by the enzyme from C1 to be inferred and a reaction sequence for cleavage of both rings of 1,8-cineole to be proposed. It provides an explanation for the reported isolation of ()-5,5-dimethyl-4-(3′-oxobutyl)-4,5-dihydrofuran-2(3H)-one from culture media of grown with 1,8-cineole.


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