Bacterial dehydrogenases

Some enzymes use other cofactors, e.g., pyrroloquinoline quinone (methoxatin). which has been found in methanol dehydrogenase and several other bacterial dehydrogenases in recent years325. 

Covalent quinoproteins possess protein-derived cofactors derived from aromatic amino acid residues. These enzymes contain a posttranslationally modified tyrosine or tryptophan residue into which one or two oxygens has been incorporated (Figure 3). In some cases, the quinolated amino acid residue is also covalently cross-linked to another amino acid residue on the polypeptide. Tyrosine-derived quinone cofactors occur in oxidases from bacterial, mammalian, and plant sources. Tryptophan-derived quinone cofactors have been found thus far in bacterial dehydrogenases. 

Nitro groups in the furan ring are reduced easily by various biochemical processes . Nitrofurazone can function as an electron acceptor in a number of bacterial dehydrogenase systems involved in carbohydrate metabolism. 

Iron Sulfur Compounds. Many molecular compounds (18—20) are known in which iron is tetrahedraHy coordinated by a combination of thiolate and sulfide donors. Of the 10 or more stmcturaHy characterized classes of Fe—S compounds, the four shown in Figure 1 are known to occur in proteins. The mononuclear iron site REPLACE occurs in the one-iron bacterial electron-transfer protein mbredoxin. The [2Fe—2S] (10) and [4Fe—4S] (12) cubane stmctures are found in the 2-, 4-, and 8-iron ferredoxins, which are also electron-transfer proteins. The [3Fe—4S] voided cubane stmcture (11) has been found in some ferredoxins and in the inactive form of aconitase, the enzyme which catalyzes the stereospecific hydration—rehydration of citrate to isocitrate in the Krebs cycle. In addition, enzymes are known that contain either other types of iron sulfur clusters or iron sulfur clusters that include other metals. Examples include nitrogenase, which reduces N2 to NH at a MoFe Sg homocitrate cluster carbon monoxide dehydrogenase, which assembles acetyl-coenzyme A (acetyl-CoA) at a FeNiS site and hydrogenases, which catalyze the reversible reduction of protons to hydrogen gas. 

The first step in the complete biodegradation of primary alcohol sulfates seems to be the hydrolysis to yield alcohol. Sulfatases are able to hydrolyze primary alcohol sulfates. Different authors have isolated and used several sulfia-tase enzymes belonging to Pseudomonas species. The alcohol obtained as a result of the hydrolysis, provided that dehydrogenases have been removed to avoid the oxidation of the alcohol, was identified by chromatography and other methods [388-394]. The absence of oxygen uptake in the splitting of different primary alcohol sulfates also confirms the hydrolysis instead of oxidation [395, 396]. The hydrolysis may acidify the medium and stop the bacterial growth in the absence of pH control [397-399]. 

Koenig K, JR Andreesen (1990) Xanthine dehydrogenase and 2-furoyl-coenzyme A dehydrogenase from Pseudomonasputida Ful two molybdenum-containing dehydrogenases of novel structural composition. J Bacterial 172 5999-6009. 

Nagy 1, G Schools, F Compermolle, P Proost, J Vanderleyden, R De Mot (1995b) Degradation of the thiocar-bamate herbicide EPTC S-ethyl dipropylcarbamoylthioate and biosafening by Rhodococcus sp. strain N186/21 involve an inducible cytochrome P-450 system and aldehyde dehydrogenase. J Bacterial 177 676-687. 

Self WT (2002) Regulation of purine hydroxylase and xanthine dehydrogenase from Clostridium purinolyti-cum in response to purines, selenium and molybdenum. J Bacterial 184 2039-2044. 

Svetlitchnyi V, C Peschel, G Acker, O Meyer (2001) Two membrane-associated NiFeS-carbon monoxide dehydrogenases from the anaerobic carbon-monoxide-utilizing eubacterium Carboxydothermus hydrogeno-formans. J Bacterial 183 5134-5144. 

Anthony C (1992) The structure of bacterial quinoprotein dehydrogenases. Int J Biochem 24 29-39. 

Hensgens CMH, J Vonck, J Van Beeumen, EFJ van Bruggen, TA Hansen (1993) Purification and characterization of an oxygen-labile, NAD-dependent alcohol dehydrogenase from Desulfovibrio gigas. J Bacterial 175 2859-2863. 

Singer ME, WR Einnerty (1985b) Alcohol dehydrogenases in Acinetobacter sp. strain HOl-N role in hexa-decane and hexadecanol metabolism. J Bacterial 164 1017-1024. 

Rogers JE, DT Gibson (1977) Purification and properties of cw-toluene dihydrodiol dehydrogenase from Pseudomonas putida. J Bacterial 130 1117-1124. 

Gescher J, W Ismail, E Olgeschlager, W Eisenreich, J Wort, G Fuchs (2006) Aerobic benzoyl-coenzyme A (Co A) catabolic pathway in Azoarcus evansii conversion of ring cleavage product by 3,4-dehydroadipyl-CoA semialdehyde dehydrogenase. J Bacterial 188 2919-2927. 

Xi H, BL Schneider, L Reitzer (2000) Purine catabolism in Escherichia coli and function of xanthine dehydrogenase in purine salvage J Bacterial 182 5332-5341. 

Sugimoto M, M Tanaba, M Hataya, S Enokibara, JA Duine, F Kawai (2001) The first step in polyethylene glycol degradation by sphingomonads proceeds via a flavoprotein alcohol dehydrogenase containing flavin adenine dinucleotide. J Bacterial 183 6694-6698. 

The bioluminescent determinations of ethanol, sorbitol, L-lactate and oxaloacetate have been performed with coupled enzymatic systems involving the specific suitable enzymes (Figure 5). The ethanol, sorbitol and lactate assays involved the enzymatic oxidation of these substrates with the concomitant reduction of NAD+ in NADH, which is in turn reoxidized by the bioluminescence bacterial system. Thus, the assay of these compounds could be performed in a one-step procedure, in the presence of NAD+ in excess. Conversely, the oxaloacetate measurement involved the simultaneous consumption of NADH by malate dehydrogenase and bacterial oxidoreductase and was therefore conducted in two steps. 

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