Cyclohexanone oxygenases from Nocardia globerula CL1 and Acinetobacter NCIB 9571 have been purified 12‐fold and 35‐fold respectively and each gives a single symmetrical sedimentation peak in the ultracentrifuge and a single protein band on 2.25 nm average pore radius polyacrylamide gels. The enzyme from N. globerula has a molecular weight of 53000 while that from Acinetobacter has a molecular weight of about 59000. Each is a single polypeptide chain with one mole of bound FAD per mole of protein that does not dissociate during purification. Acidification of the Acinetobacter enzyme in the presence of (NH4)2SO4 releases the bound FAD and yields native apoenzyme from which the active holoenzyme can be reconstituted. The apparent dissociation constant for the FAD is 40 nM. The near unitary stoichiometry of cyclohexanone, NADPH and oxygen consumption is typical of mixed function oxygenases with external electron donors. The oxygenated product has been identified as 1‐oxa‐2‐oxocycloheptane thus placing these enzymes in the small group of lactone and ester‐forming oxygenases. Their correct systematic name is cyclohexanone. NADPH: oxygen oxidoreductase (1,2‐lactonizing) (EC 1.14.13.‐). A functionally essential sulfhydryl group is present at the catalytic centre of both enzymes but there is no reliable indication from inhibitor studies that they contain any functional metal ion. The three titratable sulfhydryl groups of the Acinetobacter enzyme are not equivalent since reaction with one of them selectively inhibits catalytic activity. Protection against sulfhydryl active agents is afforded by NADPH but not by cyclohexanone. The N. globerula enzyme has a pH optimum of 8.4, apparent Km values of 1.56 μM and 31.3 μM for cyclohexanone and NADPH respectively and a catalytic centre activity of 1018 ml substrate transformed × mol enzyme−1× min−1. The Acinetobacter enzyme has a pH optimum of 9.0, apparent Km values of 6.9 tM and 17.8 μM and a catalytic centre activity of 1390 mol × mol enzyme−1× min−1. Both enzymes display absolute specificity for electron donor which contrasts with the broad specificity for ketone substrate. An enzyme‐cyclohexanone complex has been detected by difference spectroscopy only in the case of the Nocardia enzyme. Rapid reduction of the enzyme‐bound FAD occurs upon addition of NADPH in the absence of cyclohexanone. Titration of enzyme with NADPH under anaerobic conditions and anaerobic photoreduction in the presence of EDTA have not revealed the formation of any stable flavin semiquinones. These enzymes bear a strong resemblance to several of the monooxygenases that hydroxylate aromatic compounds.

Recombinant human interferon gamma (rIFN-gamma) was used for the treatment of 16 patients with various stages of cutaneous T-cell lymphoma (CTCL). All patients had been previously treated with standard topical and/or systemic therapies, and some had received experimental treatment with retinoids, recombinant human interferon alfa-2a (rIFN-alpha 2a), or radiolabeled monoclonal antibodies; most patients had an advanced stage of disease. Objective partial responses (PRs) were noted in five patients (31%) and lasted 3 months to greater than 32 months (median, 10 mo). One of these five patients had previously had disease progression after an initial PR with rIFN-alpha 2a. Six other patients (38%) showed minor or mixed responses. The most common side effects of rIFN-gamma included fever, weight loss, mild neutropenia, elevated lactate dehydrogenase, and elevated hepatic transaminases. Additionally, one episode of nephrotic syndrome and one cutaneous allergic reaction were noted. None of the toxic effects were life threatening, and all were reversible. These results suggest that rIFN-gamma has efficacy in the treatment of CTCL refractory to rIFN-alpha 2a.

Although the H2 subclass of histamine receptor has been revealed by classical pharmacological approaches, the direct identification of this adenylate cyclase-linked receptor has, despite much effort, remained elusive. Initial studies using 3H-metiamide and 3H-histamine and, subsequently, work from our own laboratory and others using 3H-cimetidine and 3H-ranitidine in various tissues, has shown the unsuitability of these ligands for labelling the H2 receptor. We report here our results using 3H-tiotidine, a more potent H2-antagonist than either cimetidine or ranitidine, and show that this ligand meets the criteria for labeling the H2 receptor in guinea pig cerebral cortex membranes.

1. Nocardia globerula CL1, isolated by enrichment on cyclohexanol and grown with it as carbon source, oxidized it with a Q(o2) of 39mul/h per mg dry wt. and the overall consumption of 2.2mumol of oxygen/mol of substrate. Cyclohexanone, 2-hydroxycyclohexan-1-one dimer and cyclohexane-1,2-dione were oxidized with Q(o2) values similar to that for cyclohexanol whereas in-caprolactone and 6-hydroxycaproate were oxidized very slowly and adipate not all. 2. Disrupted cell suspensions could not be shown to catalyse the conversion of cyclohexanol into cyclohexanone. 3. A cyclohexanol-induced cyclohexanone oxygenase (specific activity 0.55mumol of NADPH oxidized/min per mg of protein) catalysed the consumption of 1mol of NADPH and 1mol of O(2) in the presence of 1mol of cyclohexanone. NADPH oxidation did not occur under anaerobic conditions. The only detected reaction product with 25000g supernatant was 6-hydroxycaproate. 4. Extracts of cyclohexanol-grown cells contained a lactone hydrolase (specific activity 15.6mumol hydrolysed/min per mg of protein), which converted in-caprolactone into 6-hydroxycaproate. 5. Incubation of 6-hydroxycaproate with 25000g supernatant in the presence of NAD(+) resulted in NAD(+) reduction under anaerobic conditions, oxygen consumption under aerobic conditions and the conversion of 6-hydroxycaproate into adipate. 6. Cyclohexanone oxygenase fractions devoid of in-caprolactone hydrolase catalysed the stoicheiometric formation of in-caprolactone from cyclohexanone in the presence of excess of NADPH. 7. The reaction sequence for the oxidation of cyclohexanone by N. globerula CL1 is: cyclohexanol --> cyclohexanone --> in-caprolactone --> 6-hydroxycaproate --> adipate. 8. It is suggested that the adipate may be further dissimilated by beta-oxidation.

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