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In the small town where I live, just south of Hull, every house is being networked by underground full-fibre cables installed by Kcom (the privatised company stemming originally from Hull Corporation telephones). Moreover, Kcom isn't the only supplier of competing fibre networks. Don't forget local broadband providers In Issue 607's "Question of the Fortnight" ("Will you get full-fibre broadband sooner than expected?". [Extracted from the article]

1. A mono-oxygenase, which oxidizes trimethylamine and other tertiary amines bearing methyl or ethyl groups, was partially purified sixfold from Pseudomonas aminovorans grown on trimethylamine as sole carbon source. 2. The preferred electron donor was NADPH. The enzyme had a pH optimum of 8.0–9.4 for trimethylamine oxidation, and 8.8–9.2 for dimethylamine oxidation. 3. The oxidation product of trimethylamine was shown to be trimethylamine N-oxide. Other tertiary amines were probably also converted into N-oxides. 4. The enzyme also oxidized secondary amines. 5. The oxidation of trimethylamine was only slightly inhibited by CO and not at all by KCN or proadifen hydrochloride (SKF 525-A), but was inhibited by trimethylsulphonium chloride, tetramethylammonium chloride, 2,4-dichloro-6-phenylphenoxyethylamine (Lilly 53325) and its NN-diethyl derivative (Lilly 18947). 6. The oxidation of dimethylamine showed a similar response to inhibitors and a parallel loss in activity on heating at 35°C. 7. The activities of the trimethylamine mono-oxygenase, trimethylamine N-oxide demethylase and the secondary-amine mono-oxygenase increased severalfold during adaptation of succinate-grown bacteria to growth on trimethylamine, and the trimethylamine mono-oxygenase was the first enzyme to show an increase in activity. It is concluded that all three enzymes are involved in growth on trimethylamine by this organism.

1. The yeast Candida boidinii was grown on glucose as carbon source with a range of amines and amino acids as nitrogen sources. Cells grown on amines contained elevated activities of catalase. If the amines contained N-methyl groups, formaldehyde dehydrogenase, formate dehydrogenase and S-formylglutathione hydrolase were also elevated in activity compared with cells grown on (NH4)2SO4. 2. Cells grown on all the amines tested, but not those grown on urea or amino acids, contained an oxidase attacking primary amines, which is referred to as methylamine oxidase. In addition, cells grown on some amines contained a second amine oxidase, which is referred to as benzylamine oxidase. 3. Both amine oxidases were purified to near homogeneity. 4. Benzylamine oxidase was considerably more stable at 45 and 50°C than was methylamine oxidase. 5. Both enzymes had a pH optimum in the region of 7.0, and had a considerable number of substrates in common. There were, however, significant differences in the substrate specificity of the two enzymes. The ratio V/Kapp.m increased with increasing n-alkyl carbon chain length for benzylamine oxidase, but decreased for methylamine oxidase. 6. Both enzymes showed similar sensitivity to carbonyl-group reagents, copper-chelating agents and other typical ‘diamine oxidase inhibitors’. 7. The stoicheiometry for the reaction catalysed by each enzyme was established. 8. The kinetics of methylamine oxidase were examined by varying the methylamine and oxygen concentrations in turn. A non-Ping Pong kinetic pattern with intersecting double-reciprocal plots was obtained, giving Km values of 10mum for O2 and 198mum for methylamine. The significance of this unusual kinetic behaviour is discussed. Similar experiments were not possible with the benzylamine oxidase, because it seemed to have an even lower Km for O2. 9. Both enzymes had similar subunit Mr values of about 80000, but the benzylamine oxidase behaved as if it were usually a dimer, Mr 136000, which under certain conditions aggregated to a tetramer, Mr 288000. Methylamine oxidase was mainly in the form of an octamer, Mr 510000, which gave rise quite readily to dimers of Mr 150000, and on gel filtration behaved as if the Mr was 286000.