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Sharon I, Hilvert D, Schmeing TM. Cyanophycin and its biosynthesis: not hot but very cool. Nat Prod Rep 2023; 40:1479-1497. [PMID: 37231979 DOI: 10.1039/d2np00092j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Covering: 1878 to early 2023Cyanophycin is a biopolymer consisting of a poly-aspartate backbone with arginines linked to each Asp sidechain through isopeptide bonds. Cyanophycin is made by cyanophycin synthetase 1 or 2 through ATP-dependent polymerization of Asp and Arg, or β-Asp-Arg, respectively. It is degraded into dipeptides by exo-cyanophycinases, and these dipeptides are hydrolyzed into free amino acids by general or dedicated isodipeptidase enzymes. When synthesized, chains of cyanophycin coalesce into large, inert, membrane-less granules. Although discovered in cyanobacteria, cyanophycin is made by species throughout the bacterial kingdom, and cyanophycin metabolism provides advantages for toxic bloom forming algae and some human pathogens. Some bacteria have developed dedicated schemes for cyanophycin accumulation and use, which include fine temporal and spatial regulation. Cyanophycin has also been heterologously produced in a variety of host organisms to a remarkable level, over 50% of the host's dry mass, and has potential for a variety of green industrial applications. In this review, we summarize the progression of cyanophycin research, with an emphasis on recent structural studies of enzymes in the cyanophycin biosynthetic pathway. These include several unexpected revelations that show cyanophycin synthetase to be a very cool, multi-functional macromolecular machine.
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Affiliation(s)
- Itai Sharon
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, QC, Canada, H3G 0B1.
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T Martin Schmeing
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, QC, Canada, H3G 0B1.
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Sharon I, Schmeing TM. Bioinformatics of cyanophycin metabolism genes and characterization of promiscuous isoaspartyl dipeptidases that catalyze the final step of cyanophycin degradation. Sci Rep 2023; 13:8314. [PMID: 37221236 DOI: 10.1038/s41598-023-34587-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 05/03/2023] [Indexed: 05/25/2023] Open
Abstract
Cyanophycin is a bacterial biopolymer used for storage of fixed nitrogen. It is composed of a backbone of L-aspartate residues with L-arginines attached to each of their side chains. Cyanophycin is produced by cyanophycin synthetase 1 (CphA1) using Arg, Asp and ATP, and is degraded in two steps. First, cyanophycinase breaks down the backbone peptide bonds, releasing β-Asp-Arg dipeptides. Then, these dipeptides are broken down into free Asp and Arg by enzymes with isoaspartyl dipeptidase activity. Two bacterial enzymes are known to possess promiscuous isoaspartyl dipeptidase activity: isoaspartyl dipeptidase (IadA) and isoaspartyl aminopeptidase (IaaA). We performed a bioinformatic analysis to investigate whether genes for cyanophycin metabolism enzymes cluster together or are spread around the microbial genomes. Many genomes showed incomplete contingents of known cyanophycin metabolizing genes, with different patterns in various bacterial clades. Cyanophycin synthetase and cyanophycinase are usually clustered together when recognizable genes for each are found within a genome. Cyanophycinase and isoaspartyl dipeptidase genes typically cluster within genomes lacking cphA1. About one-third of genomes with genes for CphA1, cyanophycinase and IaaA show these genes clustered together, while the proportion is around one-sixth for CphA1, cyanophycinase and IadA. We used X-ray crystallography and biochemical studies to characterize an IadA and an IaaA from two such clusters, in Leucothrix mucor and Roseivivax halodurans, respectively. The enzymes retained their promiscuous nature, showing that being associated with cyanophycin-related genes did not make them specific for β-Asp-Arg dipeptides derived from cyanophycin degradation.
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Affiliation(s)
- Itai Sharon
- Department of Biochemistry and Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada
| | - T Martin Schmeing
- Department of Biochemistry and Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada.
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Dumina M, Zhgun A. Thermo-L-Asparaginases: From the Role in the Viability of Thermophiles and Hyperthermophiles at High Temperatures to a Molecular Understanding of Their Thermoactivity and Thermostability. Int J Mol Sci 2023; 24:ijms24032674. [PMID: 36768996 PMCID: PMC9916696 DOI: 10.3390/ijms24032674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 01/25/2023] [Accepted: 01/28/2023] [Indexed: 02/03/2023] Open
Abstract
L-asparaginase (L-ASNase) is a vital enzyme with a broad range of applications in medicine, food industry, and diagnostics. Among various organisms expressing L-ASNases, thermophiles and hyperthermophiles produce enzymes with superior performances-stable and heat resistant thermo-ASNases. This review is an attempt to take a broader view on the thermo-ASNases. Here we discuss the position of thermo-ASNases in the large family of L-ASNases, their role in the heat-tolerance cellular system of thermophiles and hyperthermophiles, and molecular aspects of their thermoactivity and thermostability. Different types of thermo-ASNases exhibit specific L-asparaginase activity and additional secondary activities. All products of these enzymatic reactions are associated with diverse metabolic pathways and are important for mitigating heat stress. Thermo-ASNases are quite distinct from typical mesophilic L-ASNases based on structural properties, kinetic and activity profiles. Here we attempt to summarize the current understanding of the molecular mechanisms of thermo-ASNases' thermoactivity and thermostability, from amino acid composition to structural-functional relationships. Research of these enzymes has fundamental and biotechnological significance. Thermo-ASNases and their improved variants, cloned and expressed in mesophilic hosts, can form a large pool of enzymes with valuable characteristics for biotechnological application.
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Dumina M, Zhgun A, Pokrovskaya M, Aleksandrova S, Zhdanov D, Sokolov N, El’darov M. Highly Active Thermophilic L-Asparaginase from Melioribacter roseus Represents a Novel Large Group of Type II Bacterial L-Asparaginases from Chlorobi-Ignavibacteriae-Bacteroidetes Clade. Int J Mol Sci 2021; 22:13632. [PMID: 34948436 PMCID: PMC8709496 DOI: 10.3390/ijms222413632] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 12/15/2021] [Accepted: 12/17/2021] [Indexed: 02/07/2023] Open
Abstract
L-asparaginase (L-ASNase) is a biotechnologically relevant enzyme for the pharmaceutical, biosensor and food industries. Efforts to discover new promising L-ASNases for different fields of biotechnology have turned this group of enzymes into a growing family with amazing diversity. Here, we report that thermophile Melioribacter roseus from Ignavibacteriae of the Bacteroidetes/Chlorobi group possesses two L-ASNases-bacterial type II (MrAII) and plant-type (MrAIII). The current study is focused on a novel L-ASNase MrAII that was expressed in Escherichia coli, purified and characterized. The enzyme is optimally active at 70 °C and pH 9.3, with a high L-asparaginase activity of 1530 U/mg and L-glutaminase activity ~19% of the activity compared with L-asparagine. The kinetic parameters KM and Vmax for the enzyme were 1.4 mM and 5573 µM/min, respectively. The change in MrAII activity was not significant in the presence of 10 mM Ni2+, Mg2+ or EDTA, but increased with the addition of Cu2+ and Ca2+ by 56% and 77%, respectively, and was completely inhibited by Zn2+, Fe3+ or urea solutions 2-8 M. MrAII displays differential cytotoxic activity: cancer cell lines K562, Jurkat, LnCap, and SCOV-3 were more sensitive to MrAII treatment, compared with normal cells. MrAII represents the first described enzyme of a large group of uncharacterized counterparts from the Chlorobi-Ignavibacteriae-Bacteroidetes clade.
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Affiliation(s)
- Maria Dumina
- Group of Fungal Genetic Engineering, Federal Research Center “Fundamentals of Biotechnology” of the Russian Academy of Sciences, 117312 Moscow, Russia;
| | - Alexander Zhgun
- Group of Fungal Genetic Engineering, Federal Research Center “Fundamentals of Biotechnology” of the Russian Academy of Sciences, 117312 Moscow, Russia;
| | - Marina Pokrovskaya
- Laboratory of Medical Biotechnology, Institute of Biomedical Chemistry, 119121 Moscow, Russia; (M.P.); (S.A.); (D.Z.); (N.S.)
| | - Svetlana Aleksandrova
- Laboratory of Medical Biotechnology, Institute of Biomedical Chemistry, 119121 Moscow, Russia; (M.P.); (S.A.); (D.Z.); (N.S.)
| | - Dmitry Zhdanov
- Laboratory of Medical Biotechnology, Institute of Biomedical Chemistry, 119121 Moscow, Russia; (M.P.); (S.A.); (D.Z.); (N.S.)
| | - Nikolay Sokolov
- Laboratory of Medical Biotechnology, Institute of Biomedical Chemistry, 119121 Moscow, Russia; (M.P.); (S.A.); (D.Z.); (N.S.)
| | - Michael El’darov
- Group of Fungal Genetic Engineering, Federal Research Center “Fundamentals of Biotechnology” of the Russian Academy of Sciences, 117312 Moscow, Russia;
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Loch JI, Jaskolski M. Structural and biophysical aspects of l-asparaginases: a growing family with amazing diversity. IUCrJ 2021; 8:514-531. [PMID: 34258001 PMCID: PMC8256714 DOI: 10.1107/s2052252521006011] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 06/09/2021] [Indexed: 06/13/2023]
Abstract
l-Asparaginases have remained an intriguing research topic since their discovery ∼120 years ago, especially after their introduction in the 1960s as very efficient antileukemic drugs. In addition to bacterial asparaginases, which are still used to treat childhood leukemia, enzymes of plant and mammalian origin are now also known. They have all been structurally characterized by crystallography, in some cases at outstanding resolution. The structural data have also shed light on the mechanistic details of these deceptively simple enzymes. Yet, despite all this progress, no better therapeutic agents have been found to beat bacterial asparaginases. However, a new option might arise with the discovery of yet another type of asparaginase, those from symbiotic nitrogen-fixing Rhizobia, and with progress in the protein engineering of enzymes with desired properties. This review surveys the field of structural biology of l-asparaginases, focusing on the mechanistic aspects of the well established types and speculating about the potential of the new members of this amazingly diversified family.
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Affiliation(s)
- Joanna I. Loch
- Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University, Cracow, Poland
| | - Mariusz Jaskolski
- Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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6
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Nagaratnam N, Delker SL, Jernigan R, Edwards TE, Snider J, Thifault D, Williams D, Nannenga BL, Stofega M, Sambucetti L, Hsieh JJ, Flint AJ, Fromme P, Martin-Garcia JM. Structural insights into the function of the catalytically active human Taspase1. Structure 2021; 29:873-885.e5. [PMID: 33784495 DOI: 10.1016/j.str.2021.03.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 02/07/2021] [Accepted: 03/10/2021] [Indexed: 12/15/2022]
Abstract
Taspase1 is an Ntn-hydrolase overexpressed in primary human cancers, coordinating cancer cell proliferation, invasion, and metastasis. Loss of Taspase1 activity disrupts proliferation of human cancer cells in vitro and in mouse models of glioblastoma. Taspase1 is synthesized as an inactive proenzyme, becoming active upon intramolecular cleavage. The activation process changes the conformation of a long fragment at the C-terminus of the α subunit, for which no full-length structural information exists and whose function is poorly understood. We present a cloning strategy to generate a circularly permuted form of Taspase1 to determine the crystallographic structure of active Taspase1. We discovered that this region forms a long helix and is indispensable for the catalytic activity of Taspase1. Our study highlights the importance of this element for the enzymatic activity of Ntn-hydrolases, suggesting that it could be a potential target for the design of inhibitors with potential to be developed into anticancer therapeutics.
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Affiliation(s)
- Nirupa Nagaratnam
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
| | - Silvia L Delker
- Beryllium Discovery Corp., with present address of UCB Biosciences, Bedford, MA 01730, USA
| | - Rebecca Jernigan
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
| | - Thomas E Edwards
- Beryllium Discovery Corp., with present address of UCB Biosciences, Bedford, MA 01730, USA
| | - Janey Snider
- Division of Biosciences, SRI International Menlo Park, Menlo Park, CA 94025, USA
| | - Darren Thifault
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
| | - Dewight Williams
- Eyring Materials Center, Arizona State University, Tempe, AZ 85257, USA
| | - Brent L Nannenga
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA; Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287, USA
| | - Mary Stofega
- Division of Biosciences, SRI International Menlo Park, Menlo Park, CA 94025, USA
| | - Lidia Sambucetti
- Division of Biosciences, SRI International Menlo Park, Menlo Park, CA 94025, USA
| | - James J Hsieh
- Molecular Oncology, Division of Oncology, Department of Medicine, Washington University, St. Louis, MO 63110, USA
| | - Andrew J Flint
- Frederick National Lab for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA
| | - Petra Fromme
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA.
| | - Jose M Martin-Garcia
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA; Department of Crystallography and Structural Biology, Institute of Physical-Chemistry "Rocasolano", Spanish National Research Council (CSIC), Madrid 28006, Spain.
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Li W, Irani S, Crutchfield A, Hodge K, Matthews W, Patel P, Zhang YJ, Stone E. Intramolecular Cleavage of the hASRGL1 Homodimer Occurs in Two Stages. Biochemistry 2016; 55:960-9. [PMID: 26780688 DOI: 10.1021/acs.biochem.5b01157] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human asparaginase-like protein 1 (hASRGL1) is a member of the N-terminal nucleophile (Ntn) family that hydrolyzes l-asparagine and isoaspartyl-dipeptides. The nascent protein folds into an αβ-βα sandwich fold homodimer that cleaves its own peptide backbone at the G167-T168 bond, resulting in the active form of the enzyme. However, biophysical studies of hASRGL1 are difficult because of the curious fact that intramolecular cleavage of the G167-T168 peptide bond reaches only ≤50% completion. We capitalized upon our previous observation that intramolecular processing increases thermostability and developed a differential scanning fluorimetry assay that allowed direct detection of distinct processing intermediates for the first time. A kinetic analysis of these intermediates revealed that cleavage of one subunit of the hASRGL1 subunit drastically reduces the processing rate of the adjacent monomer, and a mutagenesis study showed that stabilization of the dimer interface plays a critical role in this process. We also report a comprehensive analysis of conserved active site residues and delineate their relative roles in autoprocessing and substrate hydrolysis. In addition to glycine, which was previously reported to selectively accelerate hASRGL1 cleavage, we identified several novel small molecule activators that also promote intramolecular processing. The structure-activity analysis supports the hypothesis that multiple negatively charged small molecules interact within the active site of hASRGL1 to act as a base in promoting cleavage. Overall, our investigation provides a mechanistic understanding of the maturation process of this Ntn hydrolase family member.
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Affiliation(s)
- Wenzong Li
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Seema Irani
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Amanda Crutchfield
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Kristal Hodge
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Wendy Matthews
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Pooja Patel
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Yan Jessie Zhang
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
| | - Everett Stone
- Department of Molecular Biosciences, ‡Department of Chemical Engineering, and §Institute of Cellular and Molecular Biology, University of Texas , Austin, Texas 78712, United States
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Bejger M, Imiolczyk B, Clavel D, Gilski M, Pajak A, Marsolais F, Jaskolski M. Na⁺/K⁺ exchange switches the catalytic apparatus of potassium-dependent plant L-asparaginase. ACTA ACUST UNITED AC 2014; 70:1854-72. [PMID: 25004963 DOI: 10.1107/s1399004714008700] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 04/16/2014] [Indexed: 01/03/2023]
Abstract
Plant-type L-asparaginases, which are a subclass of the Ntn-hydrolase family, are divided into potassium-dependent and potassium-independent enzymes with different substrate preferences. While the potassium-independent enzymes have already been well characterized, there are no structural data for any of the members of the potassium-dependent group to illuminate the intriguing dependence of their catalytic mechanism on alkali-metal cations. Here, three crystal structures of a potassium-dependent plant-type L-asparaginase from Phaseolus vulgaris (PvAspG1) differing in the type of associated alkali metal ions (K(+), Na(+) or both) are presented and the structural consequences of the different ions are correlated with the enzyme activity. As in all plant-type L-asparaginases, immature PvAspG1 is a homodimer of two protein chains, which both undergo autocatalytic cleavage to α and β subunits, thus creating the mature heterotetramer or dimer of heterodimers (αβ)2. The αβ subunits of PvAspG1 are folded similarly to the potassium-independent enzymes, with a sandwich of two β-sheets flanked on each side by a layer of helices. In addition to the `sodium loop' (here referred to as the `stabilization loop') known from potassium-independent plant-type asparaginases, the potassium-dependent PvAspG1 enzyme contains another alkali metal-binding loop (the `activation loop') in subunit α (residues Val111-Ser118). The active site of PvAspG1 is located between these two metal-binding loops and in the immediate neighbourhood of three residues, His117, Arg224 and Glu250, acting as a catalytic switch, which is a novel feature that is identified in plant-type L-asparaginases for the first time. A comparison of the three PvAspG1 structures demonstrates how the metal ion bound in the activation loop influences its conformation, setting the catalytic switch to ON (when K(+) is coordinated) or OFF (when Na(+) is coordinated) to respectively allow or prevent anchoring of the reaction substrate/product in the active site. Moreover, it is proposed that Ser118, the last residue of the activation loop, is involved in the potassium-dependence mechanism. The PvAspG1 structures are discussed in comparison with those of potassium-independent L-asparaginases (LlA, EcAIII and hASNase3) and those of other Ntn-hydrolases (AGA and Tas1), as well as in the light of noncrystallographic studies.
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Affiliation(s)
- Magdalena Bejger
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Barbara Imiolczyk
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Damien Clavel
- Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland
| | - Miroslaw Gilski
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | | | | | - Mariusz Jaskolski
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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Abstract
We investigated whether an uncharacterized protein from guinea pig could be the enzyme behind Kidd's serendipitous discovery, made over 60 years ago, that guinea pig serum has cell killing ability. It has been long known that an enzyme with l-asparaginase activity is responsible for cell killing, although astonishingly, its identity remains unclear. Bacterial asparaginases with similar cell killing properties have since become a mainstay therapy of certain cancers such as acute lymphoblastic leukemia. By hydrolyzing asparagine to aspartate and ammonia, these drugs deplete the asparagine present in the blood, killing cancer cells that rely on extracellular asparagine uptake for survival. However, bacterial asparaginases can elicit an adverse immune response. We propose that replacement of bacterial enzymes with the guinea pig asparaginase responsible for serum activity, by its virtue of being more closely related to human enzymes, will be less immunogenic. To this goal, we investigated whether an uncharacterized protein from guinea pig with putative asparaginase activity, which we call gpASNase3, could be that enzyme. We examined its self-activation process (gpASNase3 requires autocleavage to become active), kinetically characterized it for asparaginase and β-aspartyl dipeptidase activity, and elucidated its crystal structure in both the uncleaved and cleaved states. This work reveals that gpASNase3 is not the enzyme responsible for the antitumor effects of guinea pig serum. It exhibits a low affinity for asparagine as measured by a high Michaelis constant, KM, in the millimolar range, in contrast to the low KM (micromolar range) required for asparaginase to be effective as an anticancer agent.
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Affiliation(s)
- Amanda M Schalk
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago , 900 S. Ashland, Chicago , Illinois 60607, United States
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10
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Nomme J, Su Y, Konrad M, Lavie A. Structures of apo and product-bound human L-asparaginase: insights into the mechanism of autoproteolysis and substrate hydrolysis. Biochemistry 2012; 51:6816-26. [PMID: 22861376 DOI: 10.1021/bi300870g] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Asparaginases catalyze the hydrolysis of the amino acid asparagine to aspartate and ammonia. Bacterial asparaginases are used in cancer chemotherapy to deplete asparagine from the blood, because several hematological malignancies depend on extracellular asparagine for growth. To avoid the immune response against the bacterial enzymes, it would be beneficial to replace them with human asparaginases. However, unlike the bacterial asparaginases, the human enzymes have a millimolar K(m) value for asparagine, making them inefficient in depleting the amino acid from blood. To facilitate the development of human variants suitable for therapeutic use, we determined the structure of human l-asparaginase (hASNase3). This asparaginase is an N-terminal nucleophile (Ntn) family member that requires autocleavage between Gly167 and Thr168 to become catalytically competent. For most Ntn hydrolases, this autoproteolytic activation occurs efficiently. In contrast, hASNas3 is relatively stable in its uncleaved state, and this allowed us to observe the structure of the enzyme prior to cleavage. To determine the structure of the cleaved state, we exploited our discovery that the free amino acid glycine promotes complete cleavage of hASNase3. Both enzyme states were elucidated in the absence and presence of the product aspartate. Together, these structures provide insight into the conformational changes required for cleavage and the precise enzyme-substrate interactions. The new understanding of hASNase3 will serve to guide the design of variants that possess a decreased K(m) value for asparagine, making the human enzyme a suitable replacement for the bacterial asparaginases in cancer therapy.
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Affiliation(s)
- Julian Nomme
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607, USA
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11
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Michalska K, Hernandez-Santoyo A, Jaskolski M. The Mechanism of Autocatalytic Activation of Plant-type L-Asparaginases. J Biol Chem 2008; 283:13388-97. [DOI: 10.1074/jbc.m800746200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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12
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Wang Y, Guo HC. Crystallographic snapshot of a productive glycosylasparaginase-substrate complex. J Mol Biol 2006; 366:82-92. [PMID: 17157318 PMCID: PMC1865511 DOI: 10.1016/j.jmb.2006.09.051] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 09/02/2006] [Accepted: 09/20/2006] [Indexed: 11/18/2022]
Abstract
Glycosylasparaginase (GA) plays an important role in asparagine-linked glycoprotein degradation. A deficiency in the activity of human GA leads to a lysosomal storage disease named aspartylglycosaminuria. GA belongs to a superfamily of N-terminal nucleophile hydrolases that autoproteolytically generate their mature enzymes from inactive single chain protein precursors. The side-chain of the newly exposed N-terminal residue then acts as a nucleophile during substrate hydrolysis. By taking advantage of mutant enzyme of Flavobacterium meningosepticum GA with reduced enzymatic activity, we have obtained a crystallographic snapshot of a productive complex with its substrate (NAcGlc-Asn), at 2.0 A resolution. This complex structure provided us an excellent model for the Michaelis complex to examine the specific contacts critical for substrate binding and catalysis. Substrate binding induces a conformational change near the active site of GA. To initiate catalysis, the side-chain of the N-terminal Thr152 is polarized by the free alpha-amino group on the same residue, mediated by the side-chain hydroxyl group of Thr170. Cleavage of the amide bond is then accomplished by a nucleophilic attack at the carbonyl carbon of the amide linkage in the substrate, leading to the formation of an acyl-enzyme intermediate through a negatively charged tetrahedral transition state.
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Affiliation(s)
| | - Hwai-Chen Guo
- *Corresponding author: Hwai-Chen Guo, Department of Physiology and Biophysics, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118-2526, telephone: 617-638-4023, fax: 617-638-4041, E-mail:
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Abstract
In plants, specialized enzymes are required to catalyze the release of ammonia from asparagine, which is the main nitrogen-relocation molecule in these organisms. In addition, K+-independent plant asparaginases are also active in splitting the aberrant isoaspartyl peptide bonds, which makes these proteins important for seed viability and germination. Here, we present the crystal structure of potassium-independent L-asparaginase from yellow lupine (LlA) and confirm the classification of this group of enzymes in the family of Ntn-hydrolases. The alpha- and beta-subunits that form the mature (alphabeta)2 enzyme arise from autoproteolytic cleavage of two copies of a precursor protein. In common with other Ntn-hydrolases, the (alphabeta) heterodimer has a sandwich-like fold with two beta-sheets flanked by two layers of alpha-helices (alphabetabetaalpha). The nucleophilic Thr193 residue, which is liberated in the autocatalytic event at the N terminus of subunit beta, is part of an active site that is similar to that observed in a homologous bacterial enzyme. An unusual sodium-binding loop of the bacterial protein, necessary for proper positioning of all components of the active site, shows strictly conserved conformation and metal coordination in the plant enzyme. A chloride anion complexed in the LlA structure marks the position of the alpha-carboxylate group of the L-aspartyl substrate/product moiety. Detailed analysis of the active site suggests why the plant enzyme hydrolyzes asparagine and its beta-peptides but is inactive towards substrates accepted by similar Ntn-hydrolases, such as taspase1, an enzyme implicated in some human leukemias. Structural comparisons of LlA and taspase1 provide interesting insights into the role of small inorganic ions in the latter enzyme.
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Affiliation(s)
- Karolina Michalska
- Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland
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Azevedo RA, Lancien M, Lea PJ. The aspartic acid metabolic pathway, an exciting and essential pathway in plants. Amino Acids 2006; 30:143-62. [PMID: 16525757 DOI: 10.1007/s00726-005-0245-2] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Accepted: 06/20/2005] [Indexed: 10/24/2022]
Abstract
Aspartate is the common precursor of the essential amino acids lysine, threonine, methionine and isoleucine in higher plants. In addition, aspartate may also be converted to asparagine, in a potentially competing reaction. The latest information on the properties of the enzymes involved in the pathways and the genes that encode them is described. An understanding of the overall regulatory control of the flux through the pathways is undisputedly of great interest, since the nutritive value of all cereal and legume crops is reduced due to low concentrations of at least one of the aspartate-derived amino acids. We have reviewed the recent literature and discussed in this paper possible methods by which the concentrations of the limiting amino acids may be increased in the seeds.
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Affiliation(s)
- R A Azevedo
- Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, Brazil.
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Abstract
Proteases play key roles in many biological processes and have numerous applications in biotechnology and industry. Recent advances in the genetics, genomics and biochemistry of the halophilic Archaea provide a tremendous opportunity for understanding proteases and their function in the context of an archaeal cell. This review summarizes our current knowledge of haloarchaeal proteases and provides a reference for future research.
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Affiliation(s)
- Rosana E De Castro
- Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
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Abstract
The crystal structure of Escherichia coli isoaspartyl aminopeptidase/asparaginase (EcAIII), an enzyme belonging to the N-terminal nucleophile (Ntn)-hydrolases family, has been determined at 1.9-A resolution for a complex obtained by cocrystallization with l-aspartate, which is a product of both enzymatic reactions catalyzed by EcAIII. The enzyme is a dimer of heterodimers, (alphabeta)(2). The (alphabeta) heterodimer, which arises by autoproteolytic cleavage of the immature protein, exhibits an alphabetabetaalpha-sandwich fold, typical for Ntn-hydrolases. The asymmetric unit contains one copy of the EcAIII.Asp complex, with clearly visible l-aspartate ligands, one bound in each of the two active sites of the enzyme. The l-aspartate ligand is located near Thr(179), the N-terminal residue of subunit beta liberated in the autoproteolytic event. Structural comparisons with the free form of EcAIII reveal that there are no major rearrangements of the active site upon aspartate binding. Although the ligand binding mode is similar to that observed in an l-aspartate complex of the related enzyme human aspartylglucosaminidase, the architecture of the EcAIII active site sheds light on the question of substrate specificity and explains why EcAIII is not able to hydrolyze glycosylated asparagine substrates.
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Affiliation(s)
- Karolina Michalska
- Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan 60-780, Poland
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