Curcumin-based-fluorescent probes targeting ALDH1A3 as a promising tool for glioblastoma precision surgery and early diagnosis.

Glioblastoma (GBM) is the most aggressive primary brain tumour for which both effective treatments and efficient tools for an early-stage diagnosis are lacking. Herein, we present curcumin-based fluorescent probes that are able to bind to aldehyde dehydrogenase 1A3 (ALDH1A3), an enzyme overexpressed in glioma stem cells (GSCs) and associated with stemness and invasiveness of GBM. Two compounds are selective versus ALDH1A3, without showing any appreciable interaction with other ALDH1A isoenzymes. Indeed, their fluorescent signal is detectable only in our positive controls in vitro and absent in cells that lack ALDH1A3. Remarkably, in vivo, our Probe selectively accumulate in glioblastoma cells, allowing the identification of the growing tumour mass. The significant specificity of our compounds is the necessary premise for their further development into glioblastoma cells detecting probes to be possibly used during neurosurgical operations.

Targeting colorectal cancer with small-molecule inhibitors of ALDH1B1.

Aldehyde dehydrogenases (ALDHs) are promising cancer drug targets, as certain isoforms are required for the survival of stem-like tumor cells. We have discovered selective inhibitors of ALDH1B1, a mitochondrial enzyme that promotes colorectal and pancreatic cancer. We describe bicyclic imidazoliums and guanidines that target the ALDH1B1 active site with comparable molecular interactions and potencies. Both pharmacophores abrogate ALDH1B1 function in cells; however, the guanidines circumvent an off-target mitochondrial toxicity exhibited by the imidazoliums. Our lead isoform-selective guanidinyl antagonists of ALDHs exhibit proteome-wide target specificity, and they selectively block the growth of colon cancer spheroids and organoids. Finally, we have used genetic and chemical perturbations to elucidate the ALDH1B1-dependent transcriptome, which includes genes that regulate mitochondrial metabolism and ribosomal function. Our findings support an essential role for ALDH1B1 in colorectal cancer, provide molecular probes for studying ALDH1B1 functions and yield leads for developing ALDH1B1-targeting therapies.

Overexpression of the Aldehyde Dehydrogenase Gene ZmALDH Confers Aluminum Tolerance in Arabidopsis thaliana.

Aluminum (Al) toxicity is the main factor limiting plant growth and the yield of cereal crops in acidic soils. Al-induced oxidative stress could lead to the excessive accumulation of reactive oxygen species (ROS) and aldehydes in plants. Aldehyde dehydrogenase (ALDH) genes, which play an important role in detoxification of aldehydes when exposed to abiotic stress, have been identified in most species. However, little is known about the function of this gene family in the response to Al stress. Here, we identified an ALDH gene in maize, ZmALDH, involved in protection against Al-induced oxidative stress. Al stress up-regulated ZmALDH expression in both the roots and leaves. The expression of ZmALDH only responded to Al toxicity but not to other stresses including low pH and other metals. The heterologous overexpression of ZmALDH in Arabidopsis increased Al tolerance by promoting the ascorbate-glutathione cycle, increasing the transcript levels of antioxidant enzyme genes as well as the activities of their products, reducing MDA, and increasing free proline synthesis. The overexpression of ZmALDH also reduced Al accumulation in roots. Taken together, these findings suggest that ZmALDH participates in Al-induced oxidative stress and Al accumulation in roots, conferring Al tolerance in transgenic Arabidopsis.

Nuclear receptors NHR-49 and NHR-79 promote peroxisome proliferation to compensate for aldehyde dehydrogenase deficiency in C. elegans.

The intracellular level of fatty aldehydes is tightly regulated by aldehyde dehydrogenases to minimize the formation of toxic lipid and protein adducts. Importantly, the dysregulation of aldehyde dehydrogenases has been implicated in neurologic disorder and cancer in humans. However, cellular responses to unresolved, elevated fatty aldehyde levels are poorly understood. Here, we report that ALH-4 is a C. elegans aldehyde dehydrogenase that specifically associates with the endoplasmic reticulum, mitochondria and peroxisomes. Based on lipidomic and imaging analysis, we show that the loss of ALH-4 increases fatty aldehyde levels and reduces fat storage. ALH-4 deficiency in the intestine, cell-nonautonomously induces NHR-49/NHR-79-dependent hypodermal peroxisome proliferation. This is accompanied by the upregulation of catalases and fatty acid catabolic enzymes, as indicated by RNA sequencing. Such a response is required to counteract ALH-4 deficiency since alh-4; nhr-49 double mutant animals are sterile. Our work reveals unexpected inter-tissue communication of fatty aldehyde levels and suggests pharmacological modulation of peroxisome proliferation as a therapeutic strategy to tackle pathology related to excess fatty aldehydes.

Enhancement in the Catalytic Activity of Human Salivary Aldehyde Dehydrogenase by Alliin from Garlic: Implications in Aldehyde Toxicity and Oral Health.

BACKGROUND: Lower human salivary aldehyde dehydrogenase (hsALDH) activity increases the risk of aldehyde mediated pathogenesis including oral cancer. Alliin, the bioactive compound of garlic, exhibits many beneficial health effects. OBJECTIVE: To study the effect of alliin on hsALDH activity. METHODS: Enzyme kinetics was performed to study the effect of alliin on the activity of hsALDH. Different biophysical techniques were employed for structural and binding studies. Docking analysis was done to predict the binding region and the type of binding forces. RESULTS: Alliin enhanced the dehydrogenase activity of the enzyme. It slightly reduced the Km and significantly enhanced the Vmax value. At 1 µM alliin concentration, the initial reaction rate increased by about two times. Further, it enhanced the hsALDH esterase activity. Biophysical studies indicated a strong complex formation between the enzyme and alliin (binding constant, Kb: 2.35 ± 0.14 x 103 M-1). It changes the secondary structure of hsALDH. Molecular docking study indicated that alliin interacts to the enzyme near the substrate binding region involving some active site residues that are evolutionary conserved. There was a slight increase in the nucleophilicity of active site cysteine in the presence of alliin. Ligand efficiency metrics values indicate that alliin is an efficient ligand for the enzyme. CONCLUSION: Alliin activates the catalytic activity of the enzyme. Hence, consumption of alliincontaining garlic preparations or alliin supplements and use of alliin in pure form may lower aldehyde related pathogenesis including oral carcinogenesis.

Crystal Structure of Aldehyde Dehydrogenase 16 Reveals Trans-Hierarchical Structural Similarity and a New Dimer.

The aldehyde dehydrogenase (ALDH) superfamily is a vast group of enzymes that catalyze the NAD+-dependent oxidation of aldehydes to carboxylic acids. ALDH16 is perhaps the most enigmatic member of the superfamily, owing to its extra C-terminal domain of unknown function and the absence of the essential catalytic cysteine residue in certain non-bacterial ALDH16 sequences. Herein we report the first production of recombinant ALDH16, the first biochemical characterization of ALDH16, and the first crystal structure of ALDH16. Recombinant expression systems were generated for the bacterial ALDH16 from Loktanella sp. and human ALDH16A1. Four high-resolution crystal structures of Loktanella ALDH16 were determined. Loktanella ALDH16 is found to be a bona fide enzyme, exhibiting NAD+-binding, ALDH activity, and esterase activity. In contrast, human ALDH16A1 apparently lacks measurable aldehyde oxidation activity, suggesting that it is a pseudoenzyme, consistent with the absence of the catalytic Cys in its sequence. The fold of ALDH16 comprises three domains: NAD+-binding, catalytic, and C-terminal. The latter is unique to ALDH16 and features a Rossmann fold connected to a protruding ß-flap. The tertiary structural interactions of the C-terminal domain mimic the quaternary structural interactions of the classic ALDH superfamily dimer, a phenomenon we call "trans-hierarchical structural similarity." ALDH16 forms a unique dimer in solution, which mimics the classic ALDH superfamily dimer-of-dimer tetramer. Small-angle X-ray scattering shows that human ALDH16A1 has the same dimeric structure and fold as Loktanella ALDH16. We suggest that the Loktanella ALDH16 structure may be considered to be the archetype of the ALDH16 family.

The quaternary structure of Thermus thermophilus aldehyde dehydrogenase is stabilized by an evolutionary distinct C-terminal arm extension.

Aldehyde dehydrogenases (ALDH) form a superfamily of dimeric or tetrameric enzymes that catalyze the oxidation of a broad range of aldehydes into their corresponding carboxylic acids with the concomitant reduction of the cofactor NAD(P) into NAD(P)H. Despite their varied polypeptide chain length and oligomerisation states, ALDHs possess a conserved architecture of three domains: the catalytic domain, NAD(P)+ binding domain, and the oligomerization domain. Here, we describe the structure and function of the ALDH from Thermus thermophilus (ALDHTt) which exhibits non-canonical features of both dimeric and tetrameric ALDH and a previously uncharacterized C-terminal arm extension forming novel interactions with the N-terminus in the quaternary structure. This unusual tail also interacts closely with the substrate entry tunnel in each monomer providing further mechanistic detail for the recent discovery of tail-mediated activity regulation in ALDH. However, due to the novel distal extension of the tail of ALDHTt and stabilizing termini-interactions, the current model of tail-mediated substrate access is not apparent in ALDHTt. The discovery of such a long tail in a deeply and early branching phylum such as Deinococcus-Thermus indicates that ALDHTt may be an ancestral or primordial metabolic model of study. This structure provides invaluable evidence of how metabolic regulation has evolved and provides a link to early enzyme regulatory adaptations.

Chemoproteomics-Enabled Covalent Ligand Screening Reveals ALDH3A1 as a Lung Cancer Therapy Target.

Chemical genetics is a powerful approach for identifying therapeutically active small molecules, but identifying the mechanisms of action underlying hit compounds remains challenging. Chemoproteomic platforms have arisen to tackle this challenge and enable rapid mechanistic deconvolution of small-molecule screening hits. Here, we have screened a cysteine-reactive covalent ligand library to identify hit compounds that impair cell survival and proliferation in nonsmall cell lung carcinoma cells, but not in primary human bronchial epithelial cells. Through this screen, we identified a covalent ligand hit, DKM 3-42, which impaired both in situ and in vivo lung cancer pathogenicity. We used activity-based protein profiling to discover that the primary target of DKM 3-42 was the catalytic cysteine in aldehyde dehydrogenase 3A1 (ALDH3A1). We performed further chemoproteomics-enabled covalent ligand screening directly against ALDH3A1, and identified a more potent and selective lead covalent ligand, EN40, which inhibits ALDH3A1 activity and impairs lung cancer pathogenicity. We show here that ALDH3A1 represents a potentially novel therapeutic target for lung cancers that express ALDH3A1 and put forth two selective ALDH3A1 inhibitors. Overall, we show the utility of combining chemical genetics screening of covalent ligand libraries with chemoproteomic approaches to rapidly identify anticancer leads and targets.

The aldehyde dehydrogenase AldA contributes to the hypochlorite defense and is redox-controlled by protein S-bacillithiolation in Staphylococcus aureus.

Staphylococcus aureus produces bacillithiol (BSH) as major low molecular weight (LMW) thiol which functions in thiol-protection and redox-regulation by protein S-bacillithiolation under hypochlorite stress. The aldehyde dehydrogenase AldA was identified as S-bacillithiolated at its active site Cys279 under NaOCl stress in S. aureus. Here, we have studied the expression, function, redox regulation and structural changes of AldA of S. aureus. Transcription of aldA was previously shown to be regulated by the alternative sigma factor SigmaB. Northern blot analysis revealed SigmaB-independent induction of aldA transcription under formaldehyde, methylglyoxal, diamide and NaOCl stress. Deletion of aldA resulted in a NaOCl-sensitive phenotype in survival assays, suggesting an important role of AldA in the NaOCl stress defense. Purified AldA showed broad substrate specificity for oxidation of several aldehydes, including formaldehyde, methylglyoxal, acetaldehyde and glycol aldehyde. Thus, AldA could be involved in detoxification of aldehyde substrates that are elevated under NaOCl stress. Kinetic activity assays revealed that AldA is irreversibly inhibited under H2O2 treatment in vitro due to overoxidation of Cys279 in the absence of BSH. Pre-treatment of AldA with BSH prior to H2O2 exposure resulted in reversible AldA inactivation due to S-bacillithiolation as revealed by activity assays and BSH-specific Western blot analysis. Using molecular docking and molecular dynamic simulation, we further show that BSH occupies two different positions in the AldA active site depending on the AldA activation state. In conclusion, we show here that AldA is an important target for S-bacillithiolation in S. aureus that is up-regulated under NaOCl stress and functions in protection under hypochlorite stress.

Thymoquinone binds and activates human salivary aldehyde dehydrogenase: Potential therapy for the mitigation of aldehyde toxicity and maintenance of oral health.

Human salivary aldehyde dehydrogenase (hsALDH) is a very important anti-oxidant enzyme present in the saliva. It is involved in the detoxification of toxic aldehydes and maintenance of oral health. Reduced level of hsALDH activity is a risk factor for oral cancer development. Thymoquinone (TQ) has many pharmacological activities and health benefits. This study aimed to examine the activation of hsALDH by TQ. The effect of TQ on the activity and kinetics of hsALDH was studied. The binding of TQ with the enzyme was examined by different biophysical methods and molecular docking analysis. TQ enhanced the dehydrogenase activity of crude and purified hsALDH by 3.2 and 2.9 fold, respectively. The Km of the purified enzyme decreased and the Vmax increased. The esterase activity also increased by 1.2 fold. No significant change in the nucleophilicity of the catalytic cysteine residue was observed. TQ forms a strong complex with hsALDH without altering the secondary structures of the enzyme. It fits in the active site of ALDH3A1 close to Cys 243 and the other highly conserved amino acid residues which lead to enhancement of substrate binding affinity and catalytic efficiency of the enzyme. TQ is expected to give better protection from toxic aldehydes in the oral cavity and to reduce the risk of oral cancer development through the activation of hsALDH. Therefore, the addition of TQ in the diet and other oral formulations is expected to be beneficial for health.

Mechanisms of protection against irreversible oxidation of the catalytic cysteine of ALDH enzymes: Possible role of vicinal cysteines.

The catalytic mechanism of the NAD(P)+-dependent aldehyde dehydrogenases (ALDHs) involves the nucleophilic attack of the essential cysteine (Cys302, mature HsALDH2 numbering) on the aldehyde substrate. Although oxidation of Cys302 will inactivate these enzymes, it is not yet well understood how this oxidation is prevented. In this work we explore possible mechanisms of protection by systematically analyzing the reported three-dimensional structures and amino acid sequences of the enzymes of the ALDH superfamily. Specifically, we considered the Cys302 conformational space, the structure and residues conservation of the catalytic loop where Cys302 is located, the observed oxidation states of Cys302, the ability of physiological reductants to revert its oxidation, and the presence of vicinal Cys in the catalytic loop. Our analyses suggested that: 1) In the apo-enzyme, the thiol group of Cys302 is quite resistant to oxidation by ambient O2 or mild oxidative conditions, because the protein environment promotes its high pKa. 2) NAD(P)+ bound in the "hydride transfer" conformation afforded total protection against Cys302 oxidation by an unknown mechanism. 3) If formed, the Cys302-sulfenic acid is protected against irreversible oxidation. 4) Of the physiological reductant agents, the dithiol lipoic acid could reduce a sulfenic or a disulfide bond in the ALDHs active site; glutathione cannot because its thiol group cannot reach Cys302, and other physiological monothiols may be ineffective in those ALDHs where their active site cannot sterically accommodate two molecules of the monothiols. 5) Formation of the disulfides Cys301-Cys302, Cys302-Cys304, Cys302-Cys305 and Cys-302-Cys306 in those ALDHs that have these Cys residues is not probable, because of the permitted Cys conformers as well as the conserved structure and low flexibility of the catalytic loop. 6) Only in some ALDH2, ALDH9, ALDH16 and ALDH23 enzymes, Cys303, alone or in conjunction with Cys301, allows disulfide formation. Interestingly, several of these enzymes are mitochondrial.

In vitro activity and stability of pure human salivary aldehyde dehydrogenase.

Human salivary aldehyde dehydrogenase (HsALDH) appears to be the first line of defence against toxic aldehydes contained in exogenous sources and is important for maintaining healthy oral cavity and protection from oral cancer. Here, the activity and stability of purified hsALDH has been determined under different conditions such as temperature, in presence of denaturants [Urea and guanidine hydrochloride (GnHCl)] and in the presence of salt (NaCl). The pure enzyme exhibited low stability when stored at room temperature (25°C) as well as at low temperature (4°C). 10% glycerol significantly improved its storage stability, particularly at 25°C. HsALDH was observed to have very low thermal stability. At higher temperatures, the enzyme gets unfolded and loses its activity quite rapidly. Further, the enzyme is unstable in the presence of denaturants like urea and GnHCl which unfold the enzyme. Salt (NaCl) has an activating effect on the enzyme, resulting from perhaps due to some conformational changes in the enzyme which facilitates the catalysis process. HsALDH proved to be a labile enzyme under in vitro conditions and certain additives like glycerol and NaCl can improve the activity/stability of the enzyme. Hence, a stabilizing agent is required to use the enzyme in in vitro studies.

Activation of Human Salivary Aldehyde Dehydrogenase by Sulforaphane: Mechanism and Significance.

Cruciferous vegetables contain the bio-active compound sulforaphane (SF) which has been reported to protect individuals against various diseases by a number of mechanisms, including activation of the phase II detoxification enzymes. In this study, we show that the extracts of five cruciferous vegetables that we commonly consume and SF activate human salivary aldehyde dehydrogenase (hsALDH), which is a very important detoxifying enzyme in the mouth. Maximum activation was observed at 1 µg/ml of cabbage extract with 2.6 fold increase in the activity. There was a ~1.9 fold increase in the activity of hsALDH at SF concentration of ≥ 100 nM. The concentration of SF at half the maximum response (EC50 value) was determined to be 52 ± 2 nM. There was an increase in the Vmax and a decrease in the Km of the enzyme in the presence of SF. Hence, SF interacts with the enzyme and increases its affinity for the substrate. UV absorbance, fluorescence and CD studies revealed that SF binds to hsALDH and does not disrupt its native structure. SF binds with the enzyme with a binding constant of 1.23 x 107 M-1. There is one binding site on hsALDH for SF, and the thermodynamic parameters indicate the formation of a spontaneous strong complex between the two. Molecular docking analysis depicted that SF fits into the active site of ALDH3A1, and facilitates the catalytic mechanism of the enzyme. SF being an antioxidant, is very likely to protect the catalytic Cys 243 residue from oxidation, which leads to the increase in the catalytic efficiency and hence the activation of the enzyme. Further, hsALDH which is virtually inactive towards acetaldehyde exhibited significant activity towards it in the presence of SF. It is therefore very likely that consumption of large quantities of cruciferous vegetables or SF supplements, through their activating effect on hsALDH can protect individuals who are alcohol intolerant against acetaldehyde toxicity and also lower the risk of oral cancer development.

Structures of Proline Utilization A (PutA) Reveal the Fold and Functions of the Aldehyde Dehydrogenase Superfamily Domain of Unknown Function.

Aldehyde dehydrogenases (ALDHs) catalyze the NAD(P)+-dependent oxidation of aldehydes to carboxylic acids and are important for metabolism and detoxification. Although the ALDH superfamily fold is well established, some ALDHs contain an uncharacterized domain of unknown function (DUF) near the C terminus of the polypeptide chain. Herein, we report the first structure of a protein containing the ALDH superfamily DUF. Proline utilization A from Sinorhizobium meliloti (SmPutA) is a 1233-residue bifunctional enzyme that contains the DUF in addition to proline dehydrogenase and l-glutamate-γ-semialdehyde dehydrogenase catalytic modules. Structures of SmPutA with a proline analog bound to the proline dehydrogenase site and NAD+ bound to the ALDH site were determined in two space groups at 1.7-1.9 Å resolution. The DUF consists of a Rossmann dinucleotide-binding fold fused to a three-stranded ß-flap. The Rossmann domain resembles the classic ALDH superfamily NAD+-binding domain, whereas the flap is strikingly similar to the ALDH superfamily dimerization domain. Paradoxically, neither structural element performs its implied function. Electron density maps show that NAD+ does not bind to the DUF Rossmann fold, and small-angle X-ray scattering reveals a novel dimer that has never been seen in the ALDH superfamily. The structure suggests that the DUF is an adapter domain that stabilizes the aldehyde substrate binding loop and seals the substrate-channeling tunnel via tertiary structural interactions that mimic the quaternary structural interactions found in non-DUF PutAs. Kinetic data for SmPutA indicate a substrate-channeling mechanism, in agreement with previous studies of other PutAs.

Targeting ALDH1A1 by disulfiram/copper complex inhibits non-small cell lung cancer recurrence driven by ALDH-positive cancer stem cells.

The existence of cancer stem cells (CSCs) in non-small cell lung cancer (NSCLC) has profound implications for cancer therapy. In this study, a disulfiram/copper (DSF/Cu) complex was evaluated in vitro and in vivo for its efficacy to inhibit CSCs, which drive recurrence of NSCLC. First, we investigated whether DSF/Cu could inhibit ALDH-positive NSCLC stem cells in vitro and tumors derived from sorted ALDH-positive CSCs in vivo. DSF/Cu (0.5/1 µmol/l) significantly inhibited the expression of stem cell transcription factors (Sox2, Oct-4 and Nanog) and reduced the capacities of NSCLC stem cells for self-renewal, proliferation and invasion in vitro. Regular injections with DSF/Cu (60/2.4 mg/kg) reduced the size of tumors derived from sorted ALDH-positive stem cells. Two other NOD/SCID xenograft models were used to determine whether DSF/Cu could target NSCLC stem cells and inhibit tumor recurrence in vivo. DSF/Cu treatment eliminated ALDH-positive cells and inhibited tumor recurrence, which was reflected by reduced tumor growth in recipient mice that were inoculated with tumor cells derived from DSF/Cu-treated cells or primary xenografts. RNA interference and overexpression of ALDH isozymes suggested that ALDH1A1, which plays a key role in ALDH-positive NSCLC stem cells, might be the target of the DSF/Cu complex. Collectively, our data demonstrate that DSF/Cu targets ALDH1A1 to inhibit NSCLC recurrence driven by ALDH-positive CSCs. Thus, the DSF/Cu complex may represent a potential therapeutic strategy for NSCLC patients.

Nicotinamide Cofactors Suppress Active-Site Labeling of Aldehyde Dehydrogenases.

Active site labeling by (re)activity-based probes is a powerful chemical proteomic tool to globally map active sites in native proteomes without using substrates. Active site labeling is usually taken as a readout for the active state of the enzyme because labeling reflects the availability and reactivity of active sites, which are hallmarks for enzyme activities. Here, we show that this relationship holds tightly, but we also reveal an important exception to this rule. Labeling of Arabidopsis ALDH3H1 with a chloroacetamide probe occurs at the catalytic Cys, and labeling is suppressed upon nitrosylation and oxidation, and upon treatment with other Cys modifiers. These experiments display a consistent and strong correlation between active site labeling and enzymatic activity. Surprisingly, however, labeling is suppressed by the cofactor NAD(+), and this property is shared with other members of the ALDH superfamily and also detected for unrelated GAPDH enzymes with an unrelated hydantoin-based probe in crude extracts of plant cell cultures. Suppression requires cofactor binding to its binding pocket. Labeling is also suppressed by ALDH modulators that bind at the substrate entrance tunnel, confirming that labeling occurs through the substrate-binding cavity. Our data indicate that cofactor binding adjusts the catalytic Cys into a conformation that reduces the reactivity toward chloroacetamide probes.

Alkynol natural products target ALDH2 in cancer cells by irreversible binding to the active site.

Falcarinol and stipudiol are natural products with potent anti-cancer activity found in several vegetables. Here, we use a chemical proteomic strategy to identify ALDH2 as a molecular target of falcarinol in cancer cells and confirm enzyme inhibition via covalent alkylation of the active site. Furthermore, the synthesis of stipudiol led to the observation that ALDH2 exhibits preference for alkynol-based binders. Inhibition of ALDH2 impairs detoxification of reactive aldehydes and limits oxidative stress response, two crucial pathways for cellular viability.

Biochemical properties of retinoid-converting enzymes and biotechnological production of retinoids.

Retinoids are a class of compounds that are forms of vitamin A and include retinal, retinol, retinoic acid, and retinyl ester. Retinal is involved in visual cycle, retinol has anti-infective, anticancer, antioxidant, and anti-wrinkle functions, and retinoic acid is used to treat acne and cancer. Retinol, retinoic acid, and retinyl ester are used in cosmetic and pharmaceutical industries. In this article, the biochemical properties and active sites and reaction mechanisms of retinoid-converting enzymes in animals and bacteria, including retinol dehydrogenase, alcohol dehydrogenase, aldo-keto reductase, and aldehyde dehydrogenase, are reviewed. The production of retinoids, using retinoid-producing enzymes and metabolically engineered cells, is also described. Uncharacterized bacterial proteins are suggested as retinoid-converting enzymes, and the production of retinoids using metabolically engineered cells is proposed as a feasible method.

Diethylaminobenzaldehyde is a covalent, irreversible inactivator of ALDH7A1.

There is growing interest in aldehyde dehydrogenases (ALDHs) because of their overexpression in cancer stem cells and the ability to mediate resistance to cancer drugs. Here, we report the first crystal structure of an aldehyde dehydrogenase complexed with the inhibitor 4-diethylaminobenzaldehyde (DEAB). Contrary to the widely held belief that DEAB is a reversible inhibitor of ALDHs, we show that DEAB irreversibly inactivates ALDH7A1 via formation of a stable, covalent acyl-enzyme species.

Single amino acid polymorphism in aldehyde dehydrogenase gene superfamily.

The aldehyde dehydrogenase gene superfamily comprises of 19 genes and 3 pseudogenes. These superfamily genes play a vital role in the formation of molecules that are involved in life processes, and detoxification of endogenous and exogenous aldehydes. ALDH superfamily genes associated mutations are implicated in various diseases, such as pyridoxine-dependent seizures, gamma-hydroxybutyric aciduria, type II Hyperprolinemia, Sjogren-Larsson syndrome including cancer and Alzheimer's disease. Accumulation of large DNA variations data especially Single Amino acid Polymorphisms (SAPs) in public databases related to ALDH superfamily genes insisted us to conduct a survey on the disease associated mutations and predict their function impact on protein structure and function. Overall this study provides an update and highlights the importance of pathogenic mutations in associated diseases. Using KD4v and Project HOPE a computational based platform, we summarized all the deleterious properties of SAPs in ALDH superfamily genes by the providing valuable insight into structural alteration rendered due to mutation. We hope this review might provide a way to define the deleteriousness of a SAP and helps to understand the molecular basis of the associated disease and also permits precise diagnosis and treatment in the near future.