Hydrogenase, presumably represented by ARUE_c26370, depends on NAD+. The genome of Arthrobacter strain Rue61a contains several genes of putative alcohol dehydrogenases and aldehyde dehydrogenases/oxidases, but since the amino acid sequence of the protein encoded by ARUE_c32130 shares 74 identity with acetaldehyde dehydrogenase II of Cupriavidus necator (formerly, Ralstonia eutropha) H16 [84], ethanol utilization by strain Rue61a likely involves this protein.Amines and other nitrogen compoundsAmong the amine compounds tested as sources of carbon and energy and as nitrogen sources, creatinine was not utilized, but creatine and sarcosine supported growth of Arthrobacter sp. Rue61a (Table 2). Creatine degradation involves hydrolysis to sarcosine (N-methylglycine) and urea by creatinase, followed by oxidation of sarcosine to formaldehyde and glycine. The gene arrangement of ARUE_c39610?9670 corresponds to that of gene clusters of Corynebacterium sp. U-96 and Arthrobacter spp. coding for serine hydroxymethyltransferase (glyA), tetrameric sarcosine oxidase (soxBDAG), serine dehydratase (sdaA), and 10-formyltetrahydrofolate deformylase (purU) [85,86], suggesting that sarcosine catabolism in Arthrobacter sp. strain Rue61a proceeds via glycine and serine to pyruvate (see Additional file 4: Figure S4). In Corynebacterium sp., the tetrameric sarcosine oxidase is the catabolic enzyme that is induced during growth on sarcosine [87]. Arthrobacter sp. strain Rue61a also grows on choline. As mentioned above, choline presumably is a source for synthesis of the osmoprotectant glycine betaine, but its utilization as carbon source probably also proceeds via glycine betaine (see Additional file 4: Figure S4). The protein encoded by ARUE_c04530, which shows 87 identity to N,N-dimethylglycine oxidase of Arthrobacter globiformis [PDB:1PJ7], is a likely candidate for the enzyme catalyzing N,N-dimethylglycine conversion to sarcosine. Agmatine seems to be utilized via the agmatine deiminase (AguA) pathway, which involves hydrolysis of agmatine to ammonia and carbamoylputrescine by AguA and another hydrolytic step to putrescine, catalyzed by N-carbamoylputrescine amidohydrolase AguB. Putrescine degradation follows oxidative deamination to 4-aminobutanal, presumably catalyzed by the ARUE_c00400 protein, which shares 76 identity with putrescine oxidase of Rhodococcus erythropolis [PDB:2YG3]. Oxidation of 4aminobutanal by -aminobutyraldehyde dehydrogenase MS-275 web produces 4-aminobutyrate, which in a transamination reaction is converted to succinic semialdehyde. Oxidationby succinate semialdehyde dehydrogenase finally yields succinic (see Additional file 4: Figure S5). Hypoxanthine and xanthine utilization by Arthobacter sp. strain Rue61a is initiated by oxidation to urate. The reaction is catalyzed by xanthine dehydrogenase or -oxidase, a molybdenum hydroxylase encoded by PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/27488460 ARUE_c35300?35310. Urate degradation probably involves urate oxidase and 5-hydroxyisourate hydrolase. The next step, catalyzed by OHCU decarboxylase, produces (S)-allantoin (see Additional file 4: Figure S6). Allantoin indeed supports growth of Arthrobacter sp. Rue61a and also can serve as sole nitrogen source. Its degradation likely occurs via glyoxylate (see Additional file 4: Figure S7). A putative allantoinase gene is located adjacent to the genes coding for glyoxylate utilization via the glycerate pathway (ARUE_c36330?6350), however, candidate genes for allantoate conversion to urea and glyoxylate, o.
