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Fitzpatrick PF, Daubner SC. Biochemical and biophysical approaches to characterization of the aromatic amino acid hydroxylases. Methods Enzymol 2024; 704:345-361. [PMID: 39300655 DOI: 10.1016/bs.mie.2024.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2024]
Abstract
The aromatic amino acid hydroxylases phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase utilize a non-heme iron to catalyze the hydroxylation of the aromatic rings of their amino acid substrates, with a tetrahydropterin serving as the source of the electrons necessary for the monooxygenation reaction. These enzymes have been subjected to a variety of biochemical and biophysical approaches, resulting in a detailed understanding of their structures and mechanism. We summarize here the experimental approaches that have led to this understanding.
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Affiliation(s)
- Paul F Fitzpatrick
- Department of Biochemistry and Structural Biology, UT Health San Antonio, San Antonio, TX, United States.
| | - S Colette Daubner
- Department of Biochemistry and Structural Biology, UT Health San Antonio, San Antonio, TX, United States
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Fitzpatrick PF. The aromatic amino acid hydroxylases: Structures, catalysis, and regulation of phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase. Arch Biochem Biophys 2023; 735:109518. [PMID: 36639008 DOI: 10.1016/j.abb.2023.109518] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 01/01/2023] [Accepted: 01/06/2023] [Indexed: 01/12/2023]
Abstract
The aromatic amino acid hydroxylases phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylase are non-heme iron enzymes that catalyze key physiological reactions. This review discusses the present understanding of the common catalytic mechanism of these enzymes and recent advances in understanding the relationship between their structures and their regulation.
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Affiliation(s)
- Paul F Fitzpatrick
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, 78229, USA.
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Li M, Subedi BP, Fitzpatrick PF, Emerson JP. Thermodynamics of iron, tetrahydrobiopterin, and phenylalanine binding to phenylalanine hydroxylase from Chromobacterium violaceum. Arch Biochem Biophys 2022; 729:109378. [PMID: 35995215 PMCID: PMC10184773 DOI: 10.1016/j.abb.2022.109378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/13/2022] [Accepted: 08/16/2022] [Indexed: 11/02/2022]
Abstract
Phenylalanine hydroxylase (PheH) is a pterin-dependent, mononuclear nonheme iron(II) oxygenase that uses the oxidative power of O2 to hydroxylate phenylalanine to form tyrosine. PheH is a member of a superfamily of O2-activating enzymes that utilizes a common metal binding motif: the 2-His-1-carboxylate facial triad. Like most members of this superfamily, binding of substrates to PheH results in a reorganization of its active site to allow O2 activation. Exploring the energetics of each step before O2 activation can provide mechanistic insight into the initial steps that support the highly specific O2 activation pathway carried out by this metalloenzyme. Here the thermal stability of PheH and its substrate complexes were investigated under an anaerobic environment by using differential scanning calorimetry. In context with known binding constants for PheH, a thermodynamic cycle associated with iron(II), tetrahydrobiopterin (BH4), and phenylalanine binding to the active site was generated, showing a distinctive cooperativity between the binding of BH4 and Phe. The addition of phenylalanine and BH4 to PheH·Fe increased the stability of this enzyme (ΔTm of 8.5 (±0.7) °C with an associated δΔH of 43.0 (±2.9) kcal/mol). The thermodynamic data presented here gives insight into the complicated interactions between metal center, cofactor, and substrate, and how this interplay sets the stage for highly specific, oxidative C-H activation in this enzyme.
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Affiliation(s)
- Mingjie Li
- Department of Chemistry, Mississippi State University, Mississippi State, MS, 39762, USA
| | - Bishnu P Subedi
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Paul F Fitzpatrick
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA.
| | - Joseph P Emerson
- Department of Chemistry, Mississippi State University, Mississippi State, MS, 39762, USA.
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Peng W, Yan S, Zhang X, Liao L, Zhang J, Shaik S, Wang B. How Do Preorganized Electric Fields Function in Catalytic Cycles? The Case of the Enzyme Tyrosine Hydroxylase. J Am Chem Soc 2022; 144:20484-20494. [DOI: 10.1021/jacs.2c09263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wei Peng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Shengheng Yan
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Xuan Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Langxing Liao
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Jinyan Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, 9190407 Jerusalem, Israel
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering and Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen University, Xiamen 361005, People Republic of China
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Park J, Hong J, Seok J, Hong H, Seo H, Kim KJ. Structural studies of a novel auxiliary-domain-containing phenylalanine hydroxylase from Bacillus cereus ATCC 14579. Acta Crystallogr D Struct Biol 2022; 78:586-598. [DOI: 10.1107/s2059798322002674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 03/08/2022] [Indexed: 11/11/2022] Open
Abstract
Phenylalanine hydroxylase (PAH), which belongs to the aromatic amino-acid hydroxylase family, is involved in protein synthesis and pyomelanine production through the hydroxylation of phenylalanine to tyrosine. In this study, the crystal structure of PAH from Bacillus cereus ATCC 14579 (BcPAH) with an additional 280 amino acids in the C-terminal region was determined. The structure of BcPAH consists of three distinct domains: a core domain with two additional inserted α-helices and two novel auxiliary domains: BcPAH-AD1 and BcPAH-AD2. Structural homologues of BcPAH-AD1 and BcPAH-AD2 are known to be involved in mRNA regulation and protein–protein interactions, and thus it was speculated that BcPAH might utilize the auxiliary domains for interaction with its partner proteins. Furthermore, phylogenetic tree analysis revealed that the three-domain PAHs, including BcPAH, are completely distinctive from both conventional prokaryotic PAHs and eukaryotic PAHs. Finally, biochemical studies of BcPAH showed that BcPAH-AD1 might be important for the structural integrity of the enzyme and that BcPAH-AD2 is related to enzyme stability and/or activity. Investigations into the intracellular functions of the two auxiliary domains and the relationship between these functions and the activity of PAH are required.
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Bocanegra-Jiménez FY, Montero-Morán GM, Lara-González S. Purification and characterization of an Fe II- and α-ketoglutarate-dependent xanthine hydroxylase from Aspergillus oryzae. Protein Expr Purif 2021; 183:105862. [PMID: 33716123 DOI: 10.1016/j.pep.2021.105862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 02/13/2021] [Accepted: 02/28/2021] [Indexed: 11/29/2022]
Abstract
XanA is an FeII- and α-ketoglutarate-dependent enzyme responsible for the conversion of xanthine to uric acid. It is unique to fungi and it was first described in Aspergillus nidulans. In this work, we present the preliminary characterization of the XanA enzyme from Aspergillus oryzae, a relevant fungus in food production in Japan. The XanA protein (GenBank BAE56701.1) was expressed as a recombinant protein in Escherichia coli BL21 (DE3) Arctic cells. Initial purification assays showed low protein solubility; therefore, the buffer composition was optimized using a fluorescence-based thermal shift assay. The protein was stabilized in solution in the presence of either 600 μM xanthine, 1 M NaCl, 600 μM α-ketoglutarate or 20% glycerol, which increases the melting temperature (Tm) by 2, 4, 5 and 6 °C respectively. The XanA protein was purified by following a three-step purification protocol. The nickel affinity purified protein was subjected to ion-exchange chromatography once the N-terminal 6XHis-tag had been successfully removed, followed by size-exclusion purification. Dynamic light scattering experiments showed that the purified protein was monodisperse and behaved as a monomer in solution. Preliminary activity assays in the presence of xanthine, α-ketoglutarate, and iron suggest that the enzyme is an iron- and α-ketoglutarate-dependent xanthine dioxygenase. Furthermore, the enzyme's optimum activity conditions were determined to be 25 °C, pH of 7.2, HEPES buffer, and 1% of glycerol. In conclusion, we established the conditions to purify the XanA enzyme from A. oryzae in its active form from E. coli bacteria and determined the optimal activity conditions.
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Affiliation(s)
- Fitzya Y Bocanegra-Jiménez
- IPICYT, División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica A. C., San Luis Potosí, SLP, Mexico
| | - Gabriela M Montero-Morán
- Facultad de Ciencias Químicas, Laboratorio IBCM, Universidad Autónoma de San Luis Potosí, San Luis Potosí, SLP, Mexico
| | - Samuel Lara-González
- IPICYT, División de Biología Molecular, Instituto Potosino de Investigación Científica y Tecnológica A. C., San Luis Potosí, SLP, Mexico.
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Lacy DC. Applications of the Marcus cross relation to inner sphere reduction of O 2: implications in small-molecule activation. Inorg Chem Front 2019. [DOI: 10.1039/c9qi00828d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The Marcus cross relation is demonstrated to be applicable to inner sphere electron transfer from iron to molecular oxygen by incorporation of the Fe(iii)–O2to Fe(iii) + superoxide BDFE inKeq. A few case-studies are provided as working examples.
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Affiliation(s)
- David C. Lacy
- Department of Chemistry
- University at Buffalo
- State University of New York
- Buffalo
- USA
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Subedi BP, Fitzpatrick PF. Mutagenesis of an Active-Site Loop in Tryptophan Hydroxylase Dramatically Slows the Formation of an Early Intermediate in Catalysis. J Am Chem Soc 2018; 140:5185-5192. [PMID: 29589922 DOI: 10.1021/jacs.8b00936] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Solution studies of the aromatic amino acid hydroxylases are consistent with the FeIVO intermediate not forming until both the amino acid and tetrahydropterin substrates have bound. Structural studies have shown that the positions of active-site loops differs significantly between the free enzyme and the enzyme-amino acid-tetrahydropterin complex. In tryptophan hydroxylase (TrpH) these mobile loops contain residues 124-134 and 365-371, with a key interaction involving Ile366. The I366N mutation in TrpH results in decreases of 1-2 orders of magnitude in the kcat and kcat/ Km values. Single turnover analyses establish that the limiting rate constant for turnover is product release for the wild-type enzyme but is formation of the first detectable intermediate I in catalysis in the mutant enzyme. The mutation does not alter the kinetics of NO binding to the ternary complex nor does it uncouple FeIVO formation from amino acid hydroxylation. The effects on the kcat value of wild-type TrpH of changing viscosity are consistent with rate-limiting product release. While the effect of viscosity on the kcat/ KO2 value is small, consistent with reversible oxygen binding, the effects on the kcat/ Km values for tryptophan and the tetrahydropterin are large, with the latter value exceeding the expected limit and varying with the identity of the viscogen. In contrast, the kinetic parameters of I366N TrpH show small changes with viscosity. The results are consistent with binding of the amino acid and pterin substrate to form the ternary complex being directly coupled to closure of loops over the active site and formation of the reactive complex. The mutation destabilizes this initial event.
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Affiliation(s)
- Bishnu P Subedi
- Department of Biochemistry and Structural Biology , University of Texas Health Science Center at San Antonio , San Antonio , Texas 78229 , United States
| | - Paul F Fitzpatrick
- Department of Biochemistry and Structural Biology , University of Texas Health Science Center at San Antonio , San Antonio , Texas 78229 , United States
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Tidemand KD, Peters GH, Harris P, Stensgaard E, Christensen HEM. Isoform-Specific Substrate Inhibition Mechanism of Human Tryptophan Hydroxylase. Biochemistry 2017; 56:6155-6164. [PMID: 29035515 DOI: 10.1021/acs.biochem.7b00763] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tryptophan hydroxylase (TPH) catalyzes the initial and rate-limiting step in the biosynthesis of serotonin, which is associated with a variety of disorders such as depression and irritable bowel syndrome. TPH exists in two isoforms: TPH1 and TPH2. TPH1 catalyzes the initial step in the synthesis of serotonin in the peripheral tissues, while TPH2 catalyzes this step in the brain. In this study, the steady-state kinetic mechanism for the catalytic domain of human TPH1 has been determined. Varying substrate tryptophan (Trp) and tetrahydrobiopterin (BH4) results in a hybrid Ping Pong-ordered mechanism in which the reaction can either occur through a Ping Pong or a sequential mechanism depending on the concentration of tryptophan. The catalytic domain of TPH1 shares a sequence identity of 81% with TPH2. Despite the high sequence identity, differences in the kinetic parameters of the isoforms have been identified; i.e., only TPH1 displays substrate tryptophan inhibition. This study demonstrates that the difference can be traced to an active site loop which displays different properties in the TPH isoforms. Steady-state kinetic results of the isoforms, and variants with point mutations in a loop lining the active site, show that the kinetic parameters of only TPH1 are significantly changed upon mutations. Mutations in the active site loop of TPH1 result in an increase in the substrate inhibition constant, Ki, and therefore turnover rate. Molecular dynamics simulations reveal that this substrate inhibition mechanism occurs through a closure of the cosubstrate, BH4, binding pocket, which is induced by Trp binding.
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Affiliation(s)
- Kasper D Tidemand
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Günther H Peters
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Pernille Harris
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Eva Stensgaard
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
| | - Hans E M Christensen
- Department of Chemistry, Technical University of Denmark , Kemitorvet 207, DK-2800 Kongens Lyngby, Denmark
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