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Query: KEGG:D02011 (FAD)
 5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycerol is catabolized in Aspergillus nidulans by glycerol kinase and a mitochondrial FAD-dependent sn-glycerol 3-phosphate dehydrogenase. The levels of both enzymes are controlled by carbon catabolite repression and by specific induction. Biochemical and genetical analyses show that dihydroxyacetone and D-glyceraldehyde are converted into glycerol and then catabolized by the same pathway. D-Glyceraldehyde can be reduced by NADP(+)-dependent glycerol dehydrogenase or by alcohol dehydrogenase I, while dihydroxyacetone is only reduced by the first enzyme. Three new glycerol non-utilizing mutants have been found. These three mutations define three hitherto unknown loci, glcE, glcF and glcG. The mutation in glcG leads to a greatly decreased sn-glycerol-3-phosphate dehydrogenase activity.
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PMID:Glycerol catabolism in Aspergillus nidulans. 203 81

Two different membrane-bound enzymes oxidizing D-sorbitol are found in Gluconobacter frateurii THD32: pyroloquinoline quinone-dependent glycerol dehydrogenase (PQQ-GLDH) and FAD-dependent D-sorbitol dehydrogenase (FAD-SLDH). In this study, FAD-SLDH appeared to be induced by L-sorbose. A mutant defective in both enzymes grew as well as the wild-type strain did, indicating that both enzymes are dispensable for growth on D-sorbitol. The strain defective in PQQ-GLDH exhibited delayed L-sorbose production, and lower accumulation of it, corresponding to decreased oxidase activity for D-sorbitol in spite of high D-sorbitol dehydrogenase activity, was observed. In the mutant strain defective in PQQ-GLDH, oxidase activity with D-sorbitol was much more resistant to cyanide, and the H(+)/O ratio was lower than in either the wild-type strain or the mutant strain defective in FAD-SLDH. These results suggest that PQQ-GLDH connects efficiently to cytochrome bo(3) terminal oxidase and that it plays a major role in L-sorbose production. On the other hand, FAD-SLDH linked preferably to the cyanide-insensitive terminal oxidase, CIO.
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PMID:Distinct physiological roles of two membrane-bound dehydrogenases responsible for D-sorbitol oxidation in Gluconobacter frateurii. 1832 43

We isolated thermotolerant Gluconobacter strains that are able to produce 5-keto-d-gluconic acid (5KGA) at 37 degrees C, a temperature at which regular mesophilic 5KGA-producing strains showed much less growth and 5KGA production. The thermotolerant strains produced 2KGA as the major product at both 30 and 37 degrees C. The amount of ketogluconates produced at 37 degrees C was slightly less than the amount produced at 30 degrees C. To improve the yield of 5KGA in these strains, we disrupted flavin adenine dinucleotide-gluconate dehydrogenase (FAD-GADH), which is responsible for 2KGA production. Genes for FAD-GADH were cloned by using inverse PCR and an in vitro cloning strategy. The sequences obtained for three thermotolerant strains were identical and showed high levels of identity to the FAD-GADH sequence reported for the genome of Gluconobacter oxydans 621 H. A kanamycin resistance gene cassette was used to disrupt the FAD-GADH genes in the thermotolerant strains. The mutant strains produced 5KGA exclusively, and the final yields were over 90% at 30 degrees C and 50% at 37 degrees C. We found that the activity of pyrroloquinoline quinone (PQQ)-dependent glycerol dehydrogenase, which is responsible for 5KGA production, increased in response to addition of PQQ and CaCl(2) in vitro when cells were grown at 37 degrees C. Addition of 5 mM CaCl(2) to the culture medium of the mutant strains increased 5KGA production to the point where over 90% of the initial substrate was converted. The thermotolerant Gluconobacter strains that we isolated in this study provide a promising new option for industrial 5KGA production.
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PMID:Screening of thermotolerant Gluconobacter strains for production of 5-keto-D-gluconic acid and disruption of flavin adenine dinucleotide-containing D-gluconate dehydrogenase. 1941 30

Acetic acid bacteria (AAB) are known for rapid and incomplete oxidation of an extensively variety of alcohols and carbohydrates, resulting in the accumulation of organic acids as the final products. These oxidative fermentations in AAB are catalyzed by PQQ- or FAD- dependent membrane-bound dehydrogenases. In the present study, the enzyme activity of the membrane-bound dehydrogenases [membrane-bound PQQ-glucose dehydrogenase (mGDH), D-gluconate dehydrogenase (GADH) and membrane-bound glycerol dehydrogenase (GLDH)] involved in the oxidation of D-glucose and D-gluconic acid (GA) was determined in six strains of three different species of AAB (three natural and three type strains). Moreover, the effect of these activities on the production of related metabolites [GA, 2-keto-D-gluconic acid (2KGA) and 5-keto-D-gluconic acid (5KGA)] was analyzed. The natural strains belonging to Gluconobacter showed a high mGDH activity and low activity in GADH and GLDH, whereas the Acetobacter malorum strain presented low activity in the three enzymes. Nevertheless, no correlation was observed between the activity of these enzymes and the concentration of the corresponding metabolites. In fact, all the tested strains were able to oxidize D-glucose to GA, being maximal at the late exponential phase of the AAB growth (24 h), which coincided with D-glucose exhaustion and the maximum mGDH activity. Instead, only some of the tested strains were capable of producing 2KGA and/or 5KGA. In the case of Gluconobacter oxydans strains, no 2KGA production was detected which is related to the absence of GADH activity after 24 h, while in the remaining strains, detection of GADH activity after 24 h resulted in a high accumulation of 2KGA. Therefore, it is possible to choose the best strain depending on the desired product composition. Moreover, the sequences of these genes were used to construct phylogenetic trees. According to the sequence of gcd, gene coding for mGDH, Acetobacter and Komagataeibacter were phylogenetically more closely related each other than with Gluconobacter.
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PMID:Determination of Dehydrogenase Activities Involved in D-Glucose Oxidation in Gluconobacter and Acetobacter Strains. 2762 43