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Production of flavors from natural substrates by microbial transformation has become a growing and expanding field of study over the past decades. Vanillin, a major component of vanilla flavor, is a principal flavoring compound used worldwide. Streptomyces sp. strain V-1 is known to be one of the most promising microbial producers of natural vanillin from ferulic acid. Although identification of the microbial genes involved in the biotransformation of ferulic acid to vanillin has been previously reported, purification and detailed characterization of the corresponding enzymes with important functions have rarely been studied. In this study, we isolated and identified 2 critical genes, fcs and ech, encoding feruloyl-CoA synthetase and enoyl-CoA hydratase/aldolase, respectively, which are involved in the vanillin production from ferulic acid. Both genes were heterologously expressed in Escherichia coli, and the resting cell reactions for converting ferulic acid to vanillin were performed. The corresponding crucial enzymes, Fcs and Ech, were purified for the first time and the enzymatic activity of each purified protein was studied. Furthermore, Fcs was comprehensively characterized, at an optimal pH of 7.0 and temperature of 30°C. Kinetic constants for Fcs revealed the apparent Km, kcat, and Vmax values to be 0.35 mM, 67.7 s(-1), and 78.2 U mg(-1), respectively. The catalytic efficiency (kcat/Km) value of Fcs was 193.4 mM(-1) s(-1) for ferulic acid. The characterization of Fcs and Ech may be helpful for further research in the field of enzymatic engineering and metabolic regulation.

The ammonia-oxidizing thaumarchaeal 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB) cycle is one of the most energy-efficient CO 2 fixation cycles discovered thus far. The protein encoded by Nmar_1308 (from Nitrosopumilus maritimus SCM1) is a promiscuous enzyme that catalyzes two essential reactions within the thaumarchaeal 3HP/4HB cycle, functioning as both a crotonyl-CoA hydratase (CCAH) and 3-hydroxypropionyl-CoA dehydratase (3HPD). In performing both hydratase and dehydratase activities, Nmar_1308 reduces the total number of enzymes necessary for CO 2 fixation in Thaumarchaeota, reducing the overall cost for biosynthesis. Here, we present the first high-resolution crystal structure of this bifunctional enzyme with key catalytic residues in the thaumarchaeal 3HP/4HB pathway.

Living systems provide a promising approach to chemical synthesis, having been optimized by evolution to convert renewable carbon sources, such as glucose, into an enormous range of small molecules. However, a large number of synthetic structures can still be difficult to obtain solely from cells, such as unsubstituted hydrocarbons. In this work, we demonstrate the use of a dual cellular–heterogeneous catalytic strategy to produce olefins from glucose using a selective hydrolase to generate an activated intermediate that is readily deoxygenated. Using a new family of iterative thiolase enzymes, we genetically engineered a microbial strain that produces 4.3 ± 0.4 g l−1 of fatty acid from glucose with 86% captured as 3-hydroxyoctanoic and 3-hydroxydecanoic acids. This 3-hydroxy substituent serves as a leaving group that enables heterogeneous tandem decarboxylation–dehydration routes to olefinic products on Lewis acidic catalysts without the additional redox input required for enzymatic or chemical deoxygenation of simple fatty acids.A dual cellular-then-heterogeneous catalysis strategy has been used to produce olefins from glucose. 3-Hydroxy acids are made using an engineered microbial host. A hydrolytic step then provides the driving force for fatty acid deoxygenation by simple heterogeneous Lewis acid catalysis. This decarboxylation–dehydration route to olefinic products avoids the need for an additional redox input typically required for deoxygenation of unmodified fatty acids.

Deficiency of short-chain enoyl-CoA hydratase (ECHS1), a crucial enzyme in fatty acid metabolism through the mitochondrial β-oxidation pathway, has been strongly linked to various diseases, especially cardiomyopathy. However, the structural and biochemical mechanisms through which ECHS1 recognizes acyl-CoAs remain poorly understood. Herein, cryo-EM analysis reveals the apo structure of ECHS1 and structures of the ECHS1-crotonyl-CoA, ECHS1-acetoacetyl-CoA, ECHS1-hexanoyl-CoA, and ECHS1-octanoyl-CoA complexes at high resolutions. The mechanism through which ECHS1 recognizes its substrates varies with the fatty acid chain lengths of acyl-CoAs. Furthermore, crucial point mutations in ECHS1 have a great impact on substrate recognition, resulting in significant changes in binding affinity and enzyme activity, as do disease-related point mutations in ECHS1. The functional mechanism of ECHS1 is systematically elucidated from structural and biochemical perspectives. These findings provide a theoretical basis for subsequent work focused on determining the role of ECHS1 deficiency (ECHS1D) in the occurrence of diseases such as cardiomyopathy. The study of ECHS1 functional mechanism provides a theoretical basis for subsequent work focused on determining the role of ECHS1 deficiency (ECHS1D) in the occurrence of diseases such as cardiomyopathy.

In addition to producing lethal antibiotics, microorganisms may also use a new form of antagonistic mechanism in which signal molecules are exported to influence the gene expression and hence the ecological competence of their competitors. We report here the isolation and characterization of a novel signaling molecule, cis -2-dodecenoic acid (BDSF), from Burkholderia cenocepacia . BDSF is structurally similar to the diffusible signal factor (DSF) that is produced by the RpfF enzyme of Xanthomonas campestris . Deletion analysis demonstrated that Bcam0581 , which encodes an RpfF homologue, was essential for BDSF production. The gene is highly conserved and widespread in the Burkholderia cepacia complex. Exogenous addition of BDSF restored the biofilm and extracellular polysaccharide production phenotypes of Xanthomonas campestris pv. campestris DSF-deficient mutants, highlighting its potential role in inter-species signaling. Further analyses showed that Candida albicans germ tube formation was strongly inhibited by either coculture with B. cenocepacia or by exogenous addition of physiological relevant levels of BDSF, whereas deletion of Bcam0581 abrogated the inhibitory ability of the bacterial pathogen. As B. cenocepacia and C. albicans are frequently encountered human pathogens, identification of the BDSF signal and its activity thus provides a new insight into the molecular grounds of their antagonistic interactions whose importance to microbial ecology and pathogenesis is now becoming evident.

DspI, a putative enoyl-coenzyme A (CoA) hydratase/isomerase, was proposed to be involved in the synthesis of cis -2-decenoic acid (CDA), a quorum sensing (QS) signal molecule in the pathogen Pseudomonas aeruginosa ( P . aeruginosa ). The present study provided a structural basis for the dehydration reaction mechanism of DspI during CDA synthesis. Structural analysis reveals that Glu126, Glu146, Cys127, Cys131 and Cys154 are important for its enzymatic function. Moreover, we show that the deletion of dspI results in a remarkable decreased in the pyoverdine production, flagella-dependent swarming motility, and biofilm dispersion as well as attenuated virulence in P . aeruginosa PA14. This study thus unravels the mechanism of DspI in diffusible signal factor (DSF) CDA biosynthesis, providing vital information for developing inhibitors that interfere with DSF associated pathogenicity in P . aeruginosa .

Multifunctional enzyme, type‐1 (MFE1) catalyzes the second and third step of the β‐oxidation cycle, being, respectively, the 2E‐enoyl‐CoA hydratase (ECH) reaction (N‐terminal part, crotonase fold) and the NAD+‐dependent, 3S‐hydroxyacyl‐CoA dehydrogenase (HAD) reaction (C‐terminal part, HAD fold). Structural enzymological properties of rat MFE1 (RnMFE1) as well as of two of its variants, namely the E123A variant (a glutamate of the ECH active site is mutated into alanine) and the BCDE variant (without domain A of the ECH part), were studied, using as substrate 3S‐hydroxybutanoyl‐CoA. Protein crystallographic binding studies show the hydrogen bond interactions of 3S‐hydroxybutanoyl‐CoA as well as of its 3‐keto, oxidized form, acetoacetyl‐CoA, with the catalytic glutamates in the ECH active site. Pre‐steady state binding experiments with NAD+ and NADH show that the kon and koff rate constants of the HAD active site of monomeric RnMFE1 and the homologous human, dimeric 3S‐hydroxyacyl‐CoA dehydrogenase (HsHAD) for NAD+ and NADH are very similar, being the same as those observed for the E123A and BCDE variants. However, steady state and pre‐steady state kinetic data concerning the HAD‐catalyzed dehydrogenation reaction of the substrate 3S‐hydroxybutanoyl‐CoA show that, respectively, the kcat and kchem rate constants for conversion into acetoacetyl‐CoA by RnMFE1 (and its two variants) are about 10 fold lower as when catalyzed by HsHAD. The dynamical properties of dehydrogenases are known to be important for their catalytic efficiency, and it is discussed that the greater complexity of the RnMFE1 fold correlates with the observation that RnMFE1 is a slower dehydrogenase than HsHAD. Enzyme kinetic studies of rat multifunctional enzyme, type‐1 (RnMFE1) (monomeric, two active sites: ECH, HAD) and human 3S‐hydroxyacyl‐CoA dehydrogenase (HsHAD) (dimeric, one active site: HAD) show that RnMFE1 is a slower dehydrogenase than HsHAD. It is discussed that the different assembly and predicted different flexibility properties of MFE1 (curved arrows) and HAD are related to their different kinetic properties.

The protein sequence and structure databases are now sufficiently representative that strategies nature uses to evolve new catalytic functions can be identified. Groups of divergently related enzymes whose members catalyze different reactions but share a common partial reaction, intermediate, or transition state (mechanistically diverse superfamilies) have been discovered, including the enolase, amidohydrolase, thiyl radical, crotonase, vicinal-oxygen-chelate, and Fe-dependent oxidase superfamilies. Other groups of divergently related enzymes whose members catalyze different overall reactions that do not share a common mechanistic strategy (functionally distinct supra families) have also been identified: ( a ) functionally distinct suprafamilies whose members catalyze successive transformations in the tryptophan and histidine biosynthetic pathways and ( b ) functionally distinct suprafamilies whose members catalyze different reactions in different metabolic pathways. An understanding of the structural bases for the catalytic diversity observed in super- and suprafamilies may provide the basis for discovering the functions of proteins and enzymes in new genomes as well as provide guidance for in vitro evolution/engineering of new enzymes.

We investigated the expression of (R)-specific enoyl coenzyme A hydratase (PhaJ) in Pseudomonas putida KT2440 accumulating polyhydroxyalkanoate (PHA) from sodium octanoate in order to identify biosynthesis pathways of PHAs from fatty acids in pseudomonads. From a database search through the P. putida KT2440 genome, an additional phaJ gene homologous to phaJ4 ^sub Pa^ from Pseudomonas aeruginosa, termed phaJ4 ^sub Pp^, was identified. The gene products of phaJ1 ^sub Pp^, which was identified previously, and phaJ4 ^sub Pp^ were confirmed to be functional in recombinant Escherichia coli on PHA synthesis from sodium dodecanoate. Cytosolic proteins from P. putida grown on sodium octanoate were subjected to anion exchange chromatography and one of the eluted fractions with hydratase activity included PhaJ4^sub Pp^, as revealed by western blot analysis. These results strongly suggest that PhaJ4^sub Pp^ forms a channeling route from β-oxidation to PHA biosynthesis in P. putida. Moreover, the substrate specificity of PhaJ1^sub Pp^ was suggested to be different from that of PhaJ1^sub Pa^ from P. aeruginosa although these two proteins share 67% amino acid sequence identity.[PUBLICATION ABSTRACT]

Background Mycobacterium tuberculosis resides inside host macrophages during infection and adapts to resilient stresses generated by the host immune system. As a response, M. tuberculosis codes for short-chain dehydrogenases/reductases (SDRs). These SDRs are nicotinamide adenine dinucleotide-reliant oxidoreductases involved in cell homeostasis. The precise function of oxidoreductases in bacteria especially M. tuberculosis were not fully explored. This study aimed to know the detail functional role of one of the oxidoreductase Rv0148 in M. tuberculosis. Results In silico analysis revealed that Rv0148 interacts with Htdy (Rv3389) and the protein interactions were confirmed using far western blot. Gene knockout mutant of Rv0148 in M. tuberculosis was constructed by specialized transduction. Macrophage cell line infection with this knockout mutant showed increased expression of pro-inflammatory cytokines. This knockout mutant is sensitive to oxidative, nitrogen, redox and electron transport inhibitor stress agents. Drug susceptibility testing of the deletion mutant showed resistance to first-line drugs such as streptomycin and ethambutol and second-line aminoglycosides such as amikacin and kanamycin. Based on interactorme analysis for Rv0148 using STRING database, we identified 220 most probable interacting partners for Htdy protein. In the Rv0148 knockout mutants, high expression of htdy was observed and we hypothesize that this would have perturbed the interactome thus resulting in drug resistance. Finally, we propose that Rv0148 and Htdy are functionally interconnected and involved in drug resistance and cell homeostasis of M. tuberculosis. Conclusions Our study suggests that Rv0148 plays a significant role in various functional aspects such as intermediatory metabolism, stress, homeostasis and also in drug resistance.