The Metabolism of Cyclohexanol by Acinetobacter NCIB 9871

Abstract

Acinetobacter NCIB 9871 was isolated by elective culture on cyclohexanol and grows with this compound as sole source of carbon. It displays a restricted growth spectrum, being unable to grow on a wide range of alternative alicyclic alcohols and ketones. Cyclohexanol-grown cells oxidize the growth substrate at a rate of 230 pl of 0 2 / h per mg dry wt with the consumption of 5.65 pmol of 02/ pmol substrate. Cyclohexanone is oxidized at a similar rate with the consumption of 4.85 pmol of 02/pmol. l-Oxa-2-oxocycloheptane and 6-hydroxyhexanoate are both oxidized at the same slow rate of 44 pl of Oz/h per mg dry wt and adipate is not oxidized.Studies with cell extracts reveal the presence of inducible dehydrogenases for cyclohexanol, 6-hydroxyhexanoate and 6-oxohexanoate and a monooxygenase, that in conjunction with a lactonase converts cyclohexanone to 6-hydroxyhexanoate. The monooxygenase is therefore presumed to be of the lactone-forming type and the pathway for conversion of cyclohexanol to adipate ; cyclohexanol + cyclohexanone + 1 -oxa-2-oxocycloheptane -+ 6-hydroxyhexanoate -+ 6-oxohexanoate -+ adipate ; for which key intermediates have been identified chromatographically, is identical with the route for the oxidation of cyclohexanol by Nocardia globerula CL1.Though the metabolism of aromatic compounds has been the subject of intensive research the cycloalkanes have only recently received serious attention. Posternak et al. [l] reported that Acetobacter suboxydans growing with either isomer of cyclohexan-1 ,2-diol released 2-hydroxycyclohexan-l-one into the growth medium and Yugari [2] showed that a species of Pseudomonas oxidized trans-cyclohexan-1 ,2-diol to cyclohexan-1,2-dione which was then cleaved by the action of a hydrolase to form 6-oxbhexanoate. The metabolism of cyclohexanol by a strain of Nocardia has been shown to involve the pathway cyclohexanol + cyclohexanone + l-oxa-2-oxocycloheptane (a lactone) + 6-hydroxyhexanoate -+ adipate [3] and it has been suggested that the adipate is further metabolized by P-oxidation. Shaw [4] reported the oxidation of cyclopentanone to glutarate by several gram negative bacteria and the involvement of a lactone-forming mixed-function oxygenase in the metabolism of cyclopentanol by Pseudomonas NCIB 9872 has been described [5]. A report of the involvement of an hydroxylase in the metabolism of cyclohexanone by a strain of Nocardia has recently appeared [6] with the implied

Microbial Metabolism of Alicyclic Hydrocarbons: Isolation and Properties of a Cyclohexane-degrading Bacterium

“…The respiration and enzyme studies are consistent with a catabolic route for cyclohexane involving initial oxidation to cyclohexanol followed by degradation of cyclohexanol by the route identified in Nocardia globerula and Acinetobacter (Norris & Trudgill, 1971 ;Donoghue & Trudgill, 1975); i.e. oxidation of cyclohexanol by a dehydrogenase to cyclohexanone followed by a monooxygenase-catalysed ring insertion of oxygen to form e-caprolactone and further breakdown of the lactone to acetate and succinate via 6-hydroxycaproate and adipate.…”

Lactone-Bound Structures of Cyclohexanone Monooxygenase Provide Insight into the Stereochemistry of Catalysis

“…These enzymes have been extensively studied since the 1970s. 6,7 The BVMOs are FAD-dependent enzymes that are notable for exhibiting high stereospecificity in many cases, while still having a broad substrate spectrum, making them quite versatile. 8−13 They only require NADPH and oxygen as cosubstrates for the reaction and produce only NADP + and water as byproducts.…”

The Metabolism of trans‐Cyclohexan‐1,2‐diol by an Acinetobacter Species

“…were disrupted as previously described [7] and unbroken cells and cell debris removed by centrifugation at 35000 x g and 3 "C for 30 min.…”

“…The termination of reactions, extraction of reaction products, preparative of derivatives and chromatographic procedures were generally as described previously [7].…”

“…Gas-liquid chromatography was performed in a Packard series 7600 instrument on diglycerol and diethyleneglycol-succinate columns as previously described [7].…”