Streptomyces Aspartate Transcarbamoylase Is a Dodecamer with Dihydroorotase Activity

Hughes, Lee E.; Hooshdaran, Massoumeh Z.; O’Donovan, Gerard A.

doi:10.1007/s002849900441

Cited by 9 publications

(4 citation statements)

References 16 publications

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“…According to the way ATCase associates with other proteins, ATCase can be divided into three classes in bacteria. ATCase in class A forms a stable dodecamer complex with the active or inactive dihydroorotase (fused or non-fused), the next enzyme in the pyrimidine biosynthetic pathway [ 87 , 88 ]. ATCase in class B is also a dodecamer complex but with regulatory subunits (fused or unfused) [ 84 , 89 ].…”

Section: Cp As Carbamyl Group Donormentioning

confidence: 99%

Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets

Shi

Caldovic

Tuchman

2018

Biology

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Carbamyl phosphate (CP) is well-known as an essential intermediate of pyrimidine and arginine/urea biosynthesis. Chemically, CP can be easily synthesized from dihydrogen phosphate and cyanate. Enzymatically, CP can be synthesized using three different classes of enzymes: (1) ATP-grasp fold protein based carbamyl phosphate synthetase (CPS); (2) Amino-acid kinase fold carbamate kinase (CK)-like CPS (anabolic CK or aCK); and (3) Catabolic transcarbamylase. The first class of CPS can be further divided into three different types of CPS as CPS I, CPS II, and CPS III depending on the usage of ammonium or glutamine as its nitrogen source, and whether N-acetyl-glutamate is its essential co-factor. CP can donate its carbamyl group to the amino nitrogen of many important molecules including the most well-known ornithine and aspartate in the arginine/urea and pyrimidine biosynthetic pathways. CP can also donate its carbamyl group to the hydroxyl oxygen of a variety of molecules, particularly in many antibiotic biosynthetic pathways. Transfer of the carbamyl group to the nitrogen group is catalyzed by the anabolic transcarbamylase using a direct attack mechanism, while transfer of the carbamyl group to the oxygen group is catalyzed by a different class of enzymes, CmcH/NodU CTase, using a different mechanism involving a three-step reaction, decomposition of CP to carbamate and phosphate, transfer of the carbamyl group from carbamate to ATP to form carbamyladenylate and pyrophosphate, and transfer of the carbamyl group from carbamyladenylate to the oxygen group of the substrate. CP is also involved in transferring its phosphate group to ADP to generate ATP in the fermentation of many microorganisms. The reaction is catalyzed by carbamate kinase, which may be termed as catabolic CK (cCK) in order to distinguish it from CP generating CK. CP is a thermally labile molecule, easily decomposed into phosphate and cyanate, or phosphate and carbamate depending on the pH of the solution, or the presence of enzyme. Biological systems have developed several mechanisms including channeling between enzymes, increased affinity of CP to enzymes, and keeping CP in a specific conformation to protect CP from decomposition. CP is highly important for our health as both a lack of, or decreased, CP production and CP accumulation results in many disease conditions.

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Section: Cp As Carbamyl Group Donormentioning

confidence: 99%

Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets

Shi

Caldovic

Tuchman

2018

Biology

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“…Prokaryotic ATCases have three major types of quaternary structure. One type is a dodecameric holoenzyme, consisting of a complex of a single ATCase catalytic subunit with a single active or inactive dihydroorotase (DHOase) [ 2 , 3 , 4 ]. The second type is also dodecameric, but consists of two catalytic trimers linked by three regulatory dimers which may be either separated [ 5 ] or fused together [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

From Genome to Structure and Back Again: A Family Portrait of the Transcarbamylases

Shi

Allewell

Tuchman

2015

IJMS

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Enzymes in the transcarbamylase family catalyze the transfer of a carbamyl group from carbamyl phosphate (CP) to an amino group of a second substrate. The two best-characterized members, aspartate transcarbamylase (ATCase) and ornithine transcarbamylase (OTCase), are present in most organisms from bacteria to humans. Recently, structures of four new transcarbamylase members, N-acetyl-l-ornithine transcarbamylase (AOTCase), N-succinyl-l-ornithine transcarbamylase (SOTCase), ygeW encoded transcarbamylase (YTCase) and putrescine transcarbamylase (PTCase) have also been determined. Crystal structures of these enzymes have shown that they have a common overall fold with a trimer as their basic biological unit. The monomer structures share a common CP binding site in their N-terminal domain, but have different second substrate binding sites in their C-terminal domain. The discovery of three new transcarbamylases, l-2,3-diaminopropionate transcarbamylase (DPTCase), l-2,4-diaminobutyrate transcarbamylase (DBTCase) and ureidoglycine transcarbamylase (UGTCase), demonstrates that our knowledge and understanding of the spectrum of the transcarbamylase family is still incomplete. In this review, we summarize studies on the structures and function of transcarbamylases demonstrating how structural information helps to define biological function and how small structural differences govern enzyme specificity. Such information is important for correctly annotating transcarbamylase sequences in the genome databases and for identifying new members of the transcarbamylase family.

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“…The trimer alone is active, but two trimers readily associate with six AaeDHO chains to form a heteromeric dodecamer with enhanced thermal stability for both components (5, 6). This partnership identifies AaeATC as a type A1 aspartate transcarbamoylase (7, 8), in which the DHO subunits are active (e.g., A. aeolicus (6), Thermus aquaticus (9)). In type A2 complexes, the DHO domain is inactive and only fulfills a structural role (e.g., Pseudomonas aeruginosa (10)).…”

mentioning

confidence: 99%

Dihydroorotase from the Hyperthermophile Aquifiex aeolicus Is Activated by Stoichiometric Association with Aspartate Transcarbamoylase and Forms a One-Pot Reactor for Pyrimidine Biosynthesis

et al. 2009

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In prokaryotes, the first three enzymes in pyrimidine biosynthesis, carbamoyl phosphate synthetase (CPS), aspartate transcarbamoylase (ATC), and dihydroorotase (DHO), are commonly expressed separately and either function independently (Escherichia coli) or associate into multifunctional complexes (Aquifex aeolicus). In mammals the enzymes are expressed as a single polypeptide chain (CAD) in the order CPS-DHO-ATC and associate into a hexamer. This study presents the three-dimensional structure of the noncovalent hexamer of DHO and ATC from the hyperthermophile A. aeolicus at 2.3 Å resolution. It is the first structure of any multienzyme complex in pyrimidine biosynthesis and is a possible model for the core of mammalian CAD. The structure has citrate, a near isosteric analogue of carbamoyl aspartate, bound to the active sites of both enzymes. Three active site loops that are intrinsically disordered in the free, inactive DHO are ordered in the complex. The reorganization also changes the peptide bond between Asp153, a ligand of the single zinc atom in DHO, and Gly154, to the rare cis conformation. In the crystal structure, six DHO and six ATC chains form a hollow dodecamer, in which the 12 active sites face an internal reaction chamber that is approximately 60 Å in diameter and connected to the cytosol by narrow tunnels. The entrances and the interior of the chamber are both electropositive, which suggests that the architecture of this nanoreactor modifies the kinetics of the bisynthase, not only by steric channeling but also by preferential escape of the product, dihydroorotase, which is less negatively charged than its precursors, carbamoyl phosphate, aspartate, or carbamoyl aspartate.

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Streptomyces Aspartate Transcarbamoylase Is a Dodecamer with Dihydroorotase Activity

Cited by 9 publications

References 16 publications

Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets

Sources and Fates of Carbamyl Phosphate: A Labile Energy-Rich Molecule with Multiple Facets

From Genome to Structure and Back Again: A Family Portrait of the Transcarbamylases

Dihydroorotase from the Hyperthermophile Aquifiex aeolicus Is Activated by Stoichiometric Association with Aspartate Transcarbamoylase and Forms a One-Pot Reactor for Pyrimidine Biosynthesis

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