engineering

N-acetylglucosamine-6-phosphate deacetylase

N-acetylglucosamine-6-phosphate deacetylase is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand N-acetylglucosamine-6-phosphate deacetylase rather than just read about it. In short: In enzymology, N-acetylglucosamine-6-phosphate deacetylase (EC 3.5.1.25), also known as GlcNAc-6-phosphate deacetylase or NagA, is an enzyme that catalyzes the deacetylation of N-acetylglucosamine-6-phosphate (GlcNAc-6-P) to glucosamine-6-phosphate (GlcN-6-P): H2O + N-acetyl-D-glucosamine 6-phosphate ⇌ {\displaystyle \rightleftharpoons } acetate + D-glucosamine 6-phosphate GlcNAc-6-phosphate deacetylase is encoded b…

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Reference excerpt

In enzymology, N-acetylglucosamine-6-phosphate deacetylase (EC 3.5.1.25), also known as GlcNAc-6-phosphate deacetylase or NagA, is an enzyme that catalyzes the deacetylation of N-acetylglucosamine-6-phosphate (GlcNAc-6-P) to glucosamine-6-phosphate (GlcN-6-P):

H2O + N-acetyl-D-glucosamine 6-phosphate ⇌ {\displaystyle \rightleftharpoons } acetate + D-glucosamine 6-phosphate GlcNAc-6-phosphate deacetylase is encoded by the gene NagA. This enzyme belongs to the amidohydrolase superfamily. Amidohydrolases are a type of hydrolase that acts upon amide bonds. All members of the amidohydrolase family employ a TIM barrel structure, and a vast majority of members are metalloenzymes. The family of enzymes is important in amino acid and nucleotide metabolism as well as biodegradation of agricultural and industrial compounds. NagA participates in amino-sugar metabolism, specifically in the biosynthesis of amino-sugar-nucleotides.

Structure NagA is a homodimeric enzyme with two domains in each dimer of the structure. Each domain I comprises a (β/α)8 - barrel structural fold, also known as a TIM barrel, and contains an active site of the enzyme. Each active site consists of the catalytic site of the enzyme and the metal-binding site that are involved in substrate and metal co-factor recognition, respectively. Domain I also forms the dimeric interface with domain I of the neighboring subunit. The smaller second domain of NagA enzymes comprises a β-barrel, which potentially acts to stabilize the enzyme. While all members of the amidohydrolase superfamily employ a TIM-barrel structural fold, NagA in Escherichia coli (EcNagA) has a pseudo-TIM barrel enclosing the funnel-like catalytic site of the enzyme. The dimer structure of NagA is considered crucial for the activity and thermostability of the enzyme.

Metal-binding site Amidohydrolase enzymes can bind one, two, or three metal atoms in the active site. These metals can include Zn2+, Co2+, Fe2+, Cd2+, and others. EcNagA contains a mononuclear metal-binding site with a Zn2+ ion; in addition, EcNagA shows a phosphate ion bound at the metal-binding site. Unlike EcNagA, NagA of Mycobacterium smegmatis (MSNagA) and Bacillus subtilis (BsNagA) have binuclear metal-binding sites. MSNagA has two divalent metal ions located in each active site, which are both required for efficient catalysis and structural stability. While most other bacteria species use Zn as their metal co-factor, BsNagA utilizes iron as the predominant metal in the metal-binding site.

Catalytic-binding site Most of the active site residues of EcNagA and BsNagA are conserved and share similar structural positions. A notable difference between mycobacterial NagA enzymes and NagA enzymes from other bacterial species is the presence of a cysteine at position 131. Other bacterial species have a lysine residue at this position. This cysteine is located in the flexible loop, which prevents the physiological substrate from binding.

Mechanism The catalytic mechanism for NagA enzymes proposed utilizes nucleophilic attack via a metal-coordinated water molecule or hydroxide ion. The mechanism proceeds via a strictly conserved active-site aspartic acid residue (Asp-273) that acts initially as a base to activate the hydrolytic water molecule in order to attack the carbonyl group of the substrate. Asp-273 then acts as an acid to protonate the amine leaving group. One proposed mechanism using the BsNagA and its two iron co-factors in the metal-binding site demonstrates the nucleophilic attack by an Fe-bridged hydroxide and then the stabilization of the carbonyl oxygen by one of the two Fe atoms.

Biological Function NagA is located in the cytoplasm of the cell. N-acetylglucosamine (GlcNAc) enters the cell as part of the breakdown of the cell wall. GlcNAc, a monosaccharide and derivative of glucose, is part of a biopolymer in the bacterial cell wall. This biopolymer forms a layered structure called peptidoglycan (PG). GlcNAc is then converted into GlcNAc-6-P by the enzyme NagE. This substrate is then deacetylated into acetate and GlcN-6-P by NagA. NagA is important for the production of GlcN-6-P, which is then used in two main pathways: PG recycling pathway and the glycolysis pathway.

PG recycling pathway In the PG Recycling pathway, once GlcNAc-6-P is metabolized by NagA, its product, GlcN-6-P, can then be converted to GlcN-1-P by the enzyme GlmM, followed by reacetylation and reaction with UTP by GlmU to form UDP-GlcNAc. UDP-GlcNAc is the end product of this pathway, which is then used to make glycosaminoglycans, proteoglycans, and glycolipids, which are all necessary in order to replenish PG for the cell wall. PG recycling is necessary for bacterial cells in order to ensure bacteria growth and prevent cell lysis.

Glycolysis pathway Instead of entering the PG recycling pathway, GlcN-6-P can be converted into fructose-6-phosphate by NagB. This reaction is reversible by the enzyme GlmS, an amidotransferase. The produced fructose-6-phosphate then enters the glycolysis pathway. Glycolysis catalyzes the production of pyruvate, leading to the citric acid cycle and allowing for the production of amino acids. GlcN-6-P and fructose-6-phosphate act as allosteric regulators of NagA, inhibiting further deacetylation of GlcNAc-6-P.

Disease relevance NagA is a potential drug target of Mycobacterium tuberculosis (Mtb). Eliminating NagA produces high levels of the allosteric activator GlcNAc-6-P, which prevents the production of GlcN-6-P in order to proceed with the PG recycling pathway. NagA is, therefore, at a crucial metabolic chokepoint in Mtb, representing the key enzymatic step in the generation of essential amino-sugar precursors. These precursors are required for Mtb cell wall biosynthesis and influence the PG recycling pathway. Additionally, the presence of cysteine in MSNagA's active site may represent a unique exploitative target in Mtb therapeutics.

Structural studies As of early 2019, 11 structures have been solved for this class of enzymes, with PDB accession codes PDB: 1O12, PDB: 1UN7, PDB: 1YMY, PDB: 1YRR, PDB: 2P50, PDB: 2P53, 6FV3, 6FV4, 3EGJ, 3IV8, and 2VHL.

Nomenclature The systematic name of this enzyme class is N-acetyl-D-glucosamine-6-phosphate amidohydrolase. Other names in common use include acetylglucosamine phosphate deacetylase, acetylaminodeoxyglucosephosphate acetylhydrolase, and 2-acetamido-2-deoxy-D-glucose-6-phosphate amidohydrolase.

References

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Illustrations

Worked examples

Example 1 — a first encounter with N-acetylglucosamine-6-phosphate deacetylase

Start with the simplest possible case. Write down what N-acetylglucosamine-6-phosphate deacetylase claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to N-acetylglucosamine-6-phosphate deacetylase before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about N-acetylglucosamine-6-phosphate deacetylase ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of N-acetylglucosamine-6-phosphate deacetylase

In research: N-acetylglucosamine-6-phosphate deacetylase appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses N-acetylglucosamine-6-phosphate deacetylase in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: N-acetylglucosamine-6-phosphate deacetylase is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 3.5.1, Enzymes of known structure, so understanding it makes those chapters shorter.
In everyday life: Look for N-acetylglucosamine-6-phosphate deacetylase outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is N-acetylglucosamine-6-phosphate deacetylase in simple terms?

Why does N-acetylglucosamine-6-phosphate deacetylase matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

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Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

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