scholarly journals Characterization of Novel Acyl Coenzyme A Dehydrogenases Involved in Bacterial Steroid Degradation

2015 ◽  
Vol 197 (8) ◽  
pp. 1360-1367 ◽  
Author(s):  
Amanda Ruprecht ◽  
Jaymie Maddox ◽  
Alexander J. Stirling ◽  
Nicole Visaggio ◽  
Stephen Y. K. Seah
Keyword(s):  
Active Site ◽  
Coenzyme A ◽  
Side Chain ◽  
Side Chains ◽  
Content Type ◽  
Carbon Side Chain ◽  
Acyl Coa Dehydrogenases ◽  
Acyl Coenzyme A ◽  
Rhodococcus Jostii

ABSTRACTThe acyl coenzyme A (acyl-CoA) dehydrogenases (ACADs) FadE34 and CasC, encoded by the cholesterol and cholate gene clusters ofMycobacterium tuberculosisandRhodococcus jostiiRHA1, respectively, were successfully purified. Both enzymes differ from previously characterized ACADs in that they contain two fused acyl-CoA dehydrogenase domains in a single polypeptide. Site-specific mutagenesis showed that only the C-terminal ACAD domain contains the catalytic glutamate base required for enzyme activity, while the N-terminal ACAD domain contains an arginine required for ionic interactions with the pyrophosphate of the flavin adenine dinucleotide (FAD) cofactor. Therefore, the two ACAD domains must associate to form a single active site. FadE34 and CasC were not active toward the 3-carbon side chain steroid metabolite 3-oxo-23,24-bisnorchol-4-en-22-oyl-CoA (4BNC-CoA) but were active toward steroid CoA esters containing 5-carbon side chains. CasC has similar specificity constants for cholyl-CoA, deoxycholyl-CoA, and 3β-hydroxy-5-cholen-24-oyl-CoA, while FadE34 has a preference for the last compound, which has a ring structure similar to that of cholesterol metabolites. Knockout of thecasCgene inR. jostiiRHA1 resulted in a reduced growth on cholate as a sole carbon source and accumulation of a 5-carbon side chain cholate metabolite. FadE34 and CasC represent unique members of ACADs with primary structures and substrate specificities that are distinct from those of previously characterized ACADs.IMPORTANCEWe report here the identification and characterization of acyl-CoA dehydrogenases (ACADs) involved in the metabolism of 5-carbon side chains of cholesterol and cholate. The two homologous enzymes FadE34 and CasC, fromM. tuberculosisandRhodococcus jostiiRHA1, respectively, contain two ACAD domains per polypeptide, and we show that these two domains interact to form a single active site. FadE34 and CasC are therefore representatives of a new class of ACADs with unique primary and quaternary structures. The bacterial steroid degradation pathway is important for the removal of steroid waste in the environment and for survival of the pathogenM. tuberculosiswithin host macrophages. FadE34 is a potential target for development of new antibiotics against tuberculosis.

scholarly journals FadD19 of Rhodococcus rhodochrous DSM43269, a Steroid-Coenzyme A Ligase Essential for Degradation of C-24 Branched Sterol Side Chains

2011 ◽  
Vol 77 (13) ◽  
pp. 4455-4464 ◽  
Author(s):  
M. H. Wilbrink ◽  
M. Petrusma ◽  
L. Dijkhuizen ◽  
R. van der Geize
Keyword(s):  
Mutant Strain ◽  
Coenzyme A ◽  
Side Chain ◽  
Side Chains ◽  
Rhodococcus Rhodochrous ◽  
Content Type ◽  
Coa Ligase ◽  
Coenzyme A Ligase ◽  
Sequential Inactivation

ABSTRACTThe actinobacterial cholesterol catabolic gene cluster contains a subset of genes that encode β-oxidation enzymes with a putative role in sterol side chain degradation. We investigated the physiological roles of several genes, i.e.,fadD17,fadD19,fadE26,fadE27, andro04690DSM43269, by gene inactivation studies in mutant strain RG32 ofRhodococcus rhodochrousDSM43269. Mutant strain RG32 is devoid of 3-ketosteroid 9α-hydroxylase (KSH) activity and was constructed following the identification, cloning, and sequential inactivation of fivekshAgene homologs in strain DSM43269. We show that mutant strain RG32 is fully blocked in steroid ring degradation but capable of selective sterol side chain degradation. Except for RG32ΔfadD19, none of the mutants constructed in RG32 revealed an aberrant phenotype on sterol side chain degradation compared to parent strain RG32. Deletion offadD19in strain RG32 completely blocked side chain degradation of C-24 branched sterols but interestingly not that of cholesterol. The additional inactivation offadD17in mutant RG32ΔfadD19also did not affect cholesterol side chain degradation. Heterologously expressed FadD19DSM43269nevertheless was active toward steroid-C26-oic acid substrates. Our data identified FadD19 as a steroid-coenzyme A (CoA) ligase with an essentialin vivorole in the degradation of the side chains of C-24 branched-chain sterols. This paper reports the identification and characterization of a CoA ligase with anin vivorole in sterol side chain degradation. The high similarity (67%) between the FadD19DSM43269and FadD19H37Rvenzymes further suggests that FadD19H37Rvhas anin vivorole in sterol metabolism ofMycobacterium tuberculosisH37Rv.

scholarly journals A Novel Steroid-Coenzyme A Ligase from Novosphingobium sp. Strain Chol11 Is Essential for an Alternative Degradation Pathway for Bile Salts

2017 ◽  
Vol 84 (1) ◽  
Author(s):  
Onur Yücel ◽  
Johannes Holert ◽  
Kevin Christopher Ludwig ◽  
Sven Thierbach ◽  
Bodo Philipp
Keyword(s):  
Bile Salts ◽  
Coenzyme A ◽  
Alternative Pathway ◽  
Degradation Pathway ◽  
Side Chain ◽  
Side Chains ◽  
Content Type ◽  
C Cycle ◽  
Degrading Bacteria ◽  
Coenzyme A Ligase

ABSTRACT Bile salts such as cholate are steroid compounds with a C5 carboxylic side chain and occur ubiquitously in vertebrates. Upon their excretion into soils and waters, bile salts can serve as growth substrates for diverse bacteria. Novosphingobium sp. strain Chol11 degrades 7-hydroxy bile salts via 3-keto-7-deoxy-Δ4,6 metabolites by the dehydration of the 7-hydroxyl group catalyzed by the 7α-hydroxysteroid dehydratase Hsh2. This reaction has not been observed in the well-studied 9-10-seco degradation pathway used by other steroid-degrading bacteria indicating that strain Chol11 uses an alternative pathway. A reciprocal BLASTp analysis showed that known side chain degradation genes from other cholate-degrading bacteria (Pseudomonas stutzeri Chol1, Comamonas testosteroni CNB-2, and Rhodococcus jostii RHA1) were not found in the genome of strain Chol11. The characterization of a transposon mutant of strain Chol11 showing altered growth with cholate identified a novel steroid-24-oyl–coenzyme A ligase named SclA. The unmarked deletion of sclA resulted in a strong growth rate decrease with cholate, while growth with steroids with C3 side chains or without side chains was not affected. Intermediates with a 7-deoxy-3-keto-Δ4,6 structure, such as 3,12-dioxo-4,6-choldienoic acid (DOCDA), were shown to be likely physiological substrates of SclA. Furthermore, a novel coenzyme A (CoA)-dependent DOCDA degradation metabolite with an additional double bond in the side chain was identified. These results support the hypothesis that Novosphingobium sp. strain Chol11 harbors an alternative pathway for cholate degradation, in which side chain degradation is initiated by the CoA ligase SclA and proceeds via reaction steps catalyzed by so-far-unknown enzymes different from those of other steroid-degrading bacteria. IMPORTANCE This study provides further evidence of the diversity of metabolic pathways for the degradation of steroid compounds in environmental bacteria. The knowledge about these pathways contributes to the understanding of the CO2-releasing part of the global C cycle. Furthermore, it is useful for investigating the fate of pharmaceutical steroids in the environment, some of which may act as endocrine disruptors.

scholarly journals Functional Characterization of Three Specific Acyl-Coenzyme A Synthetases Involved in Anaerobic Cholesterol Degradation inSterolibacterium denitrificansChol1S

2018 ◽  
Vol 84 (7) ◽  
Author(s):  
Markus Warnke ◽  
Tobias Jung ◽  
Christian Jacoby ◽  
Michael Agne ◽  
Franziska Maria Feller ◽  
...  
Keyword(s):  
Coenzyme A ◽  
Functional Characterization ◽  
Enzymatic Reaction ◽  
Side Chain ◽  
Enzymatic Reactions ◽  
Biological Degradation ◽  
Content Type ◽  
Aldehyde Dehydrogenases ◽  
Degrading Bacteria ◽  
Acyl Coenzyme A

ABSTRACTThe denitrifying betaproteobacteriumSterolibacterium denitrificansChol1S catabolizes steroids such as cholesterol via an oxygen-independent pathway. It involves enzyme reaction sequences described for aerobic cholesterol and bile acid degradation as well as enzymes uniquely found in anaerobic steroid-degrading bacteria. Recent studies provided evidence that inS. denitrificans, the cholest-4-en-3-one intermediate is oxygen-independently oxidized to Δ4-dafachronic acid (C26-oic acid), which is subsequently activated by a substrate-specific acyl-coenzyme A (acyl-CoA) synthetase (ACS). Further degradation was suggested to proceed via unconventional β-oxidation, where aldolases, aldehyde dehydrogenases, and additional ACSs substitute for classical β-hydroxyacyl-CoA dehydrogenases and thiolases. Here, we heterologously expressed three cholesterol-induced genes that putatively code for AMP-forming ACSs and characterized two of the products as specific 3β-hydroxy-Δ5-cholenoyl-CoA (C24-oic acid)- and pregn-4-en-3-one-22-oyl-CoA (C22-oic acid)-forming ACSs, respectively. A third heterologously produced ATP-dependent ACS was inactive with C26-, C24-, or C22-oic-acids but activated 3aα-H-4α-(3′propanoate)-7aβ-methylhexahydro-1,5-indanedione (HIP) to HIP-CoA, a rather late intermediate of aerobic cholesterol degradation that still contains the CD rings of the sterane skeleton. This work provides experimental evidence that anaerobic steroid degradation proceeds via numerous alternate CoA-ester-dependent or -independent enzymatic reaction sequences as a result of aldolytic side chain and hydrolytic sterane ring C—C bond cleavages. The aldolytic side chain degradation pathway comprising highly exergonic ACSs and aldehyde dehydrogenases is considered to be essential for driving the unfavorable oxygen-independent C26hydroxylation forward.IMPORTANCEThe biological degradation of ubiquitously abundant steroids is hampered by their low solubility and the presence of two quaternary carbon atoms. The degradation of cholesterol by aerobicActinobacteriahas been studied in detail for more than 30 years and involves a number of oxygenase-dependent reactions. In contrast, much less is known about the oxygen-independent degradation of steroids in denitrifying bacteria. In the cholesterol-degrading anaerobic model organismSterolibacterium denitrificansChol1S, initial evidence has been obtained that steroid degradation proceeds via numerous alternate coenzyme A (CoA)-ester-dependent/independent reaction sequences. Here, we describe the heterologous expression of three highly specific and characteristic acyl-CoA synthetases, two of which play key roles in the degradation of the side chain, whereas a third one is specifically involved in the B ring degradation. The results obtained shed light into oxygen-independent steroid degradation comprising more than 40 enzymatic reactions.

scholarly journals A Pathway for Degradation of Uracil to Acetyl Coenzyme A in Bacillus megaterium

2020 ◽  
Vol 86 (7) ◽  
Author(s):  
Di Zhu ◽  
Yifeng Wei ◽  
Jinyu Yin ◽  
Dazhi Liu ◽  
Ee Lui Ang ◽  
...  
Keyword(s):  
Energy Source ◽  
Bacillus Megaterium ◽  
Coenzyme A ◽  
Catabolic Pathway ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Content Type ◽  
Biochemical Pathways ◽  
Acetyl Coenzyme

ABSTRACT Bacteria utilize diverse biochemical pathways for the degradation of the pyrimidine ring. The function of the pathways studied to date has been the release of nitrogen for assimilation. The most widespread of these pathways is the reductive pyrimidine catabolic pathway, which converts uracil into ammonia, carbon dioxide, and β-alanine. Here, we report the characterization of a β-alanine:pyruvate aminotransferase (PydD2) and an NAD+-dependent malonic semialdehyde dehydrogenase (MSDH) from a reductive pyrimidine catabolism gene cluster in Bacillus megaterium. Together, these enzymes convert β-alanine into acetyl coenzyme A (acetyl-CoA), a key intermediate in carbon and energy metabolism. We demonstrate the growth of B. megaterium in defined medium with uracil as its sole carbon and energy source. Homologs of PydD2 and MSDH are found in association with reductive pyrimidine pathway genes in many Gram-positive bacteria in the order Bacillales. Our study provides a basis for further investigations of the utilization of pyrimidines as a carbon and energy source by bacteria. IMPORTANCE Pyrimidine has wide occurrence in natural environments, where bacteria use it as a nitrogen and carbon source for growth. Detailed biochemical pathways have been investigated with focus mainly on nitrogen assimilation in the past decades. Here, we report the discovery and characterization of two important enzymes, PydD2 and MSDH, which constitute an extension for the reductive pyrimidine catabolic pathway. These two enzymes, prevalent in Bacillales based on our bioinformatics studies, allow stepwise conversion of β-alanine, a previous “end product” of the reductive pyrimidine degradation pathway, to acetyl-CoA as carbon and energy source.

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