Phosphoserine aminotransferase has conserved active site from microbes to higher eukaryotes with minor deviations

2021 ◽  
Vol 28 ◽  
Author(s):  
Rohit Kumar Singh ◽  
Devbrat Kumar ◽  
Samudrala Gourinath
Keyword(s):  
Cancer Progression ◽  
Active Site ◽  
Enzyme Analysis ◽  
Active Site Residues ◽  
Tail Region ◽  
Phosphoserine Aminotransferase ◽  
Structural Work ◽  
Colon Cancer Progression ◽  
Functional Defect ◽  
Living Organisms

: Serine is ubiquitously synthesized in all living organisms from the glycolysis intermediate 3-phosphoglycerate (PGA) by phosphoserine biosynthetic pathway, consisting of three different enzymes, namely: 3-phosphoglycerate dehydrogenase (PGDH), phosphoserine aminotransferase (PSAT), and phosphoserine phosphatase (PSP). Any functional defect or mutation in these enzymes may cause deliberating conditions, such as colon cancer progression and chemoresistance in humans. Phosphoserine aminotransferase (PSAT) is the second enzyme in this pathway that converts phosphohydroxypyruvate (PHP) to O-phospho-L-serine (OPLS). Humans encode two isoforms of this enzyme: PSAT1 and PSAT2. PSAT1 exists as a functional dimer, where each protomer has a large and a small domain; each large domain contains a Lys residue that covalently binds PLP. The PLP-binding site of human PSAT1 and most of its active site residues are highly conserved in all known PSAT structures except for Cys-80. Interestingly, Two PSAT structures from different organisms show halide binding near their active site. While the human PSAT1 shows a water molecule at this site with different interacting residues, suggesting the inability of halide binding in the human enzyme. Analysis of the human PSAT1 structure showed a big patch of positive charge around the active site, in contrast to the bacterial PSATs. Compared to human PSAT1, the PSAT2 isoform lacks 46 residues at its C-terminal tail. This tail region is present at the opening of the active site as observed in the other PSAT structures. Further structural work on human PSAT2 may reveal the functional importance of these 46 residues.

scholarly journals Ferrochelatase: the convergence of the porphyrin biosynthesis and iron transport pathways

2011 ◽  
Vol 15 (05n06) ◽  
pp. 350-356 ◽  
Author(s):  
Gregory A. Hunter ◽  
Salam Al-Karadaghi ◽  
Gloria C. Ferreira
Keyword(s):  
Active Site ◽  
Ferrous Iron ◽  
Metal Ion ◽  
Iron Transport ◽  
Enzyme Commission Number ◽  
Metal Ion Binding ◽  
Active Site Residues ◽  
Transport Pathways ◽  
Living Organisms

Ferrochelatase (also known as PPIX ferrochelatase; Enzyme Commission number 4.9.9.1.1) catalyzes the insertion of ferrous iron into PPIX to form heme. This reaction unites the biochemically synchronized pathways of porphyrin synthesis and iron transport in nearly all living organisms. The ferrochelatases are an evolutionarily diverse family of enzymes with no more than six active site residues known to be perfectly conserved. The availability of over thirty different crystal structures, including many with bound metal ions or porphyrins, has added tremendously to our understanding of ferrochelatase structure and function. It is generally believed that ferrous iron is directly channeled to ferrochelatase in vivo, but the identity of the suspected chaperone remains uncertain despite much recent progress in this area. Identification of a conserved metal ion binding site at the base of the active site cleft may be an important clue as to how ferrochelatases acquire iron, and catalyze desolvation during transport to the catalytic site to complete heme synthesis.

Development of Xanthine Based Inhibitors Targeting Phosphodiesterase 9A

2017 ◽  
Vol 14 (10) ◽  
pp. 1122-1137 ◽  
Author(s):  
Nivedita Singh ◽  
Parameswaran Saravanan ◽  
M.S. Thakur ◽  
Sanjukta Patra
Keyword(s):  
Free Energy ◽  
Active Site ◽  
Signal Transduction Pathway ◽  
Docking Study ◽  
Primary Objective ◽  
Cgmp Level ◽  
Active Site Residues ◽  
Aromatic Fragment ◽  
Docking Approach ◽  
Free Energy Of Binding

Background: Phosphodiesterases 9A (PDE9A) is one of the prominent regulating enzymes of the signal transduction pathway having highest catalytic affinity for second messenger, cGMP. When the cGMP level is lowered, an uncontrolled expression of PDE9A may lead to various neurodegenerative diseases. To regulate the catalytic activity of PDE9A, potent inhibitors are needed. Objective: The primary objective of the present study was to develop new xanthine based inhibitors targeting PDE9A. This study was an attempt to bring structural diversification in PDE9A inhibitor development because most of the existing inhibitors are constructed over pyrazolopyrimidinone scaffold. Methods: Manual designing and parallel molecular docking approach were used for the development of xanthine derivatives. In this study, N1, N3, N9 and C8 positions of xanthine scaffold were selected as substitution sites to design 200 new compounds. Reverse docking and pharmaceutical analyses were used for final validation of most promising compounds. Results: By keeping free energy of binding cut-off of -6.0 kcal/mol, 52 compounds were screened. The compounds with substitution at N1, N3 and C8 positions of xanthine showed good occupancy in PDE9A active site pocket with a significant interaction pattern. This was further validated by screening different factors such as free energy of binding, inhibition constant and interacting active site residues in the 5Å region. Substitution at C8 position with phenyl substituent determined the inhibition affinity of compounds towards PDE9A by establishing a strong hydrophobic - hydrophobic interaction. The alkyl chain at N1 position generated selectivity of compounds towards PDE9A. The aromatic fragment at N3 position increased the binding affinity of compounds. Thus, by comparative docking study, it was found that compound 39-42 formed selective interaction towards PDE9A over other members of the PDE superfamily. Conclusion: From the present study, N1, N3 and C8 positions of xanthine were concluded as the best sites for substitution for the generation of potent PDE9A inhibitors.

Role of MicroRNAs in Colon Cancer Progression and Metastasis

2020 ◽  
Vol 20 ◽  
Author(s):  
Shruthi Sanjitha Sampath ◽  
Sivaramakrishnan Venkatabalsubramanian ◽  
Satish Ramalingam
Keyword(s):  
Colon Cancer ◽  
Cancer Progression ◽  
Target Genes ◽  
Tumour Progression ◽  
Intestinal Barrier ◽  
Colon Cancer Progression ◽  
Bowel Diseases ◽  
Inflammatory Bowel ◽  
Novel Therapeutic Strategies

: MicroRNAs regulate gene expression at the posttranscriptional level by binding to the mRNA of their target genes. The dysfunction of miRNAs is strongly associated with the inflammation of the colon. Besides, some microRNAs are shown to suppress tumours while others promote tumour progression and metastasis. Inflammatory bowel diseases include Crohn’s disease and Ulcerative colitis which increase the risk factor for inflammation-associated colon cancer. MicroRNAs are shown to be involved in gastrointestinal pathologies, by targeting the transcripts encoding proteins of the intestinal barrier and their regulators that are associated with inflammation and colon cancer. Detection of these microRNAs in the blood, serum, tissues, faecal matter, etc will enable us to use these microRNAs as biomarkers for early detection of the associated malignancies and design novel therapeutic strategies to overcome the same. Information on MicroRNAs can be applied for the development of targeted therapies against inflammation-mediated colon cancer.

Computational Analysis of miRNA and their Gene Targets Significantly Involved in Colorectal Cancer Progression

MicroRNA ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Jeyalakshmi Kandhavelu ◽  
Kumar Subramanian ◽  
Amber Khan ◽  
Aadilah Omar ◽  
Paul Ruff ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Colon Cancer ◽  
Cancer Progression ◽  
Target Prediction ◽  
Computational Prediction ◽  
Initial Step ◽  
Kegg Pathways ◽  
Candidate Mirnas ◽  
Common Cancer ◽  
Colon Cancer Progression

Background:Globally, colorectal cancer (CRC) is the third most common cancer in women and the fourth most common cancer in men. Dysregulation of small non-coding miRNAs have been correlated with colon cancer progression. Since there are increasing reports of candidate miRNAs as potential biomarkers for CRC, this makes it important to explore common miRNA biomarkers for colon cancer. As computational prediction of miRNA targets is a critical initial step in identifying miRNA: mRNA target interactions for validation, we aim here to construct a potential miRNA network and its gene targets for colon cancer from previously reported candidate miRNAs, inclusive of 10 up- and 9 down-regulated miRNAs from tissues; and 10 circulatory miRNAs. </P><P> Methods: The gene targets were predicted using DIANA-microT-CDS and TarBaseV7.0 databases. Each miRNA and its targets were analyzed further for colon cancer hotspot genes, whereupon DAVID analysis and mirPath were used for KEGG pathway analysis.Results:We have predicted 874 and 157 gene targets for tissue and serum specific miRNA candidates, respectively. The enrichment of miRNA revealed that particularly hsa-miR-424-5p, hsa-miR-96-5p, hsa-miR-1290, hsa-miR-224, hsa-miR-133a and has-miR-363-3p present possible targets for colon cancer hallmark genes, including BRAF, KRAS, EGFR, APC, amongst others. DAVID analysis of miRNA and associated gene targets revealed the KEGG pathways most related to cancer and colon cancer. Similar results were observed in mirPath analysis. A new insight gained in the colon cancer network pathway was the association of hsa-mir-133a and hsa-mir-96-5p with the PI3K-AKT signaling pathway. In the present study, target prediction shows that while hsa-mir-424-5p has an association with mostly 10 colon cancer hallmark genes, only their associations with MAP2 and CCND1 have been experimentally validated.These miRNAs and their targets require further evaluation for a better understanding of their associations, ultimately with the potential to develop novel therapeutic targets.

scholarly journals An enzymatic activation of formaldehyde for nucleotide methylation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Charles Bou-Nader ◽  
Frederick W. Stull ◽  
Ludovic Pecqueur ◽  
Philippe Simon ◽  
Vincent Guérineau ◽  
...  
Keyword(s):  
Amino Acids ◽  
Thymidylate Synthase ◽  
Active Site ◽  
De Novo ◽  
Crystallographic Structure ◽  
De Novo Synthesis ◽  
Active Site Residues ◽  
Enzymatic Activation ◽  
Enzyme Cofactors ◽  
Unique Ability

AbstractFolate enzyme cofactors and their derivatives have the unique ability to provide a single carbon unit at different oxidation levels for the de novo synthesis of amino-acids, purines, or thymidylate, an essential DNA nucleotide. How these cofactors mediate methylene transfer is not fully settled yet, particularly with regard to how the methylene is transferred to the methylene acceptor. Here, we uncovered that the bacterial thymidylate synthase ThyX, which relies on both folate and flavin for activity, can also use a formaldehyde-shunt to directly synthesize thymidylate. Combining biochemical, spectroscopic and anaerobic crystallographic analyses, we showed that formaldehyde reacts with the reduced flavin coenzyme to form a carbinolamine intermediate used by ThyX for dUMP methylation. The crystallographic structure of this intermediate reveals how ThyX activates formaldehyde and uses it, with the assistance of active site residues, to methylate dUMP. Our results reveal that carbinolamine species promote methylene transfer and suggest that the use of a CH2O-shunt may be relevant in several other important folate-dependent reactions.

scholarly journals Important Role for Phylogenetically Invariant PP2Acα Active Site and C-Terminal Residues Revealed by Mutational Analysis in Saccharomyces cerevisiae

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 21-29 ◽  
Author(s):  
David R H Evans ◽  
Brian A Hemmings
Keyword(s):  
Protein Interactions ◽  
Active Site ◽  
Protein Function ◽  
Mutational Analysis ◽  
Yeast Cells ◽  
Temperature Sensitive ◽  
Active Site Residues ◽  
Catalytic Function

Abstract PP2A is a central regulator of eukaryotic signal transduction. The human catalytic subunit PP2Acα functionally replaces the endogenous yeast enzyme, Pph22p, indicating a conservation of function in vivo. Therefore, yeast cells were employed to explore the role of invariant PP2Ac residues. The PP2Acα Y127N substitution abolished essential PP2Ac function in vivo and impaired catalysis severely in vitro, consistent with the prediction from structural studies that Tyr-127 mediates substrate binding and its side chain interacts with the key active site residues His-118 and Asp-88. The V159E substitution similarly impaired PP2Acα catalysis profoundly and may cause global disruption of the active site. Two conditional mutations in the yeast Pph22p protein, F232S and P240H, were found to cause temperature-sensitive impairment of PP2Ac catalytic function in vitro. Thus, the mitotic and cell lysis defects conferred by these mutations result from a loss of PP2Ac enzyme activity. Substitution of the PP2Acα C-terminal Tyr-307 residue by phenylalanine impaired protein function, whereas the Y307D and T304D substitutions abolished essential function in vivo. Nevertheless, Y307D did not reduce PP2Acα catalytic activity significantly in vitro, consistent with an important role for the C terminus in mediating essential protein-protein interactions. Our results identify key residues important for PP2Ac function and characterize new reagents for the study of PP2A in vivo.

scholarly journals The Collagen-Modifying Enzyme PLOD2 Is Induced and Required during L1-Mediated Colon Cancer Progression

2021 ◽  
Vol 22 (7) ◽  
pp. 3552
Author(s):  
Sanith Cheriyamundath ◽  
Anmol Kumar ◽  
Nancy Gavert ◽  
Thomas Brabletz ◽  
Avri Ben-Ze’ev
Keyword(s):  
Liver Metastasis ◽  
Cancer Progression ◽  
Cell Adhesion Molecule ◽  
Tumor Tissue ◽  
Normal Mucosa ◽  
Cell Compartment ◽  
Cellular Processes ◽  
Stem Cell Compartment ◽  
Colonic Crypts ◽  
Colon Cancer Progression

The overactivation of Wnt/b-catenin signaling is a hallmark of colorectal cancer (CRC) development. We identified the cell adhesion molecule L1CAM (L1) as a target of b-catenin-TCF transactivation in CRC cells. The overexpression of L1 in CRC cells confers enhanced proliferation, motility, tumorigenesis and liver metastasis, and L1 is exclusively localized in the invasive areas of human CRC tissue. A number of genes are induced after L1 transfection into CRC cells by a mechanism involving the cytoskeletal protein ezrin and the NF-kB pathway. When studying the changes in gene expression in CRC cells overexpressing L1 in which ezrin levels were suppressed by shRNA to ezrin, we discovered the collagen-modifying enzyme lysyl hydroxylase 2 (PLOD2) among these genes. We found that increased PLOD2 expression was required for the cellular processes conferred by L1, including enhanced proliferation, motility, tumorigenesis and liver metastasis, since the suppression of endogenous PLOD2 expression, or its enzymatic activity, blocked the enhanced tumorigenic properties conferred by L1. The mechanism involved in increased PLOD2 expression by L1 involves ezrin signaling and PLOD2 that affect the SMAD2/3 pathway. We found that PLOD2 is localized in the colonic crypts in the stem cell compartment of the normal mucosa and is found at increased levels in invasive areas of the tumor and, in some cases, throughout the tumor tissue. The therapeutic strategies to target PLOD2 expression might provide a useful approach for CRC treatment.

Sign in / Sign up

Export Citation Format

Share Document