RING-CLEAVAGE REACTIONS IN THE METABOLISM OF (-)-MENTHOL AND (-)-MENTHONE BY A CORYNEBACTERIUM SP

Corynebacterium sp. strain RWM1 grew with (-)-menthol, (-)-menthone an d other acyclic monoterpenes as sole carbon sources. Growth on menthol was very slow, with a doubling time of more than 24 h, and was not ra pid with (-)-menthone (doubling time 12 h). Concentrations of either c arbon source greater than 0.025% inhibited growth. (-)-Menthone-grown cultures transiently accumulated 3,7-dimethyl-6-hydroxyoctanoate durin g growth, and (-)-menthol-grown cells oxidized (-)-menthol, (-)-mentho ne, 3,7-dimethyl-6-octanolide and 3.7-dimethyl-6-hydroxyoctanoate. Alt hough neither a menthol oxidase nor a menthol dehydrogenase could be d etected in extracts of (-)-menthol- or (-)-menthone-grown cells, an in duced NADPH-linked monooxygenase with activity towards (-)-menthone wa s readily detected. With crude cell extracts, only 3,7-dimethyl-6-hydr oxyoctanoate was detected as the reaction product. When the (-)-mentho ne monooxygenase was separated from an induced 3.7-dimethyl-6-octanoli de hydrolase by chromatography on hydroxyapatite, the lactone 3,7-dime thyl-6-octanolide was shown to be the product of oxygenation.