Asparagine reactions

Derivation Hydrolysis of asparagine, reaction of ammonia with diethyl fumarate. 

Aspartate is involved in the control point of pyrimidine biosynthesis (Reaction 1 below), in transamination reactions (Reaction 2 below), interconversions with asparagine (reactions 3 and 4), in the metabolic pathway leading to AMP (reaction 5 below), in the urea cycle (reactions 2 and 8 below), IMP de novo biosynthesis, and is a precursor to homoserine, threonine, isoleucine, and methionine (reaction 7 below). It is also involved in the malate aspartate shuttle. 

Antineoplastic agents that cannot be grouped under subheadings 1-9 include miltefosine which is an alkylphosphocholine that is used to treat skin metastasis of breast cancer, and crispantase which breaks down asparagine to aspartic acid and ammonia. It is active against tumor cells that lack the enzyme asparaginase, such as acute lymphoblastic leukemia cells. Side effects include irritation of the skin in the case of miltefosine and anaphylactic reactions in the case of crispantase. Another recent development is the proteasome inhibitor bortezomib which is used to treat multiple myeloma. 

Figure 28-4. The asparagine synthetase reaction. Note similarities to and differences from the glutamine synthetase reaction (Figure 28-2).

Figure 4.4 Release of amino acids from cortical slices exposed to 50 mM K+. Measurements by HPEC and fluorescence detection after reaction of amino acids with o-phthalaldehyde 1, aspartate 2, glutamate 3, asparagine 4, serine 5, glutamine 6, histidine 7, homoserine (internal standard) 8, glycine 9, threonine 10, arginine 11, taurine 12, alanine 13, GABA 14, tyrosine. Glutamate concentration is almost 1 pmol/gl which represents a release rate of 30 pmol/min/mg tissue...

L-Asparaginase is an enzyme that may be produced by Escherichia coli. Asparaginase hydrolyzes the reaction of asparagines to aspartic acid and ammonia to deplete lymphoid cells of asparagine, which inhibits protein synthesis. The... 

Figure 12.14 (a) Hydrolytic reaction catalysed by L-asparaginase. (b) Reaction by which asparagine is synthesized in most mammalian cells... 

The primary limitation associated with GC/MS is the need for derivatization. Derivatization introduces additional complexity to the system and is not 100% efficient. Inefficient reactions result in the presence of multiple derivatized forms of the same compound. For example, we can detect three different derivatization products of the amino acid asparagine (mw = 132) in M. truncatula roots (Fig.3.4). These include asparagine, N,0-TMS (mw = 276), asparagine, N,N,0-TMS (mw = 348), and asparagine, N,N,N,0-TMS (mw = 420). Inefficiency of the derivation reactions also limits the lower concentration range of analytes that can be profiled. Finally, derivatization is not capable of achieving volatility for all compounds, such as many of the flavonoid glycosides. If derivatization is successful and the analyte is... 

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