Aspartic acid kinase

The answer is C. Pyruvate kinase deficiency is ruled out by the elevated serum lactate levels. The coma is associated with a fasting hypoglycemia, which is indicative of pyruvate carboxylase deficiency. The elevated citrulline and lysine in the serum are due to a reduction of aspartic acid levels, which are caused by the reduced levels of oxaloacetate, the product of the pymvate carboxylase reaction. 

The c-terminal sequence of c-fms, downstream of the kinase domain, has little homology to the PDGF receptor (13%). There are two tyrosine residues in this region at positions 924 and 970, the former being preceded by an aspartic acid residue. Feline c-fms is probably phosphorylated at four sites on tyrosine [28] but the mapping of their positions in the primary structure has not yet been published. 

In addition to the enzyme the reaction mixture contained Hepes buffer, IMP, GTP, MgCl, and creatine phosphate and phosphocreatine kinase (a regeneration system for GTP). The reaction was initiated by adding aspartic acid. Samples were removed at intervals, and the reactions were terminated by direct injection onto the HPLC column. Figure 9.113 shows chromatograms of samples removed at 0,5, and 10 minutes of incubation. The disappearance of IMP and GTP and the appearance of GTP and sAMP can be noted. 

In some cases, mutation of surface or active site residues has been required to improve stability and solubility. Mutation of surface cysteines prevented the formation of disulfide-linked aggregates in FGFRl [54]. Mutation of highly conserved, active site residues, to create a kinase-dead mutant, was required for a number of kinases whose over-expression proved to be toxic to cells. The conserved aspartic acid in the DFG motif was mutated to an asparagine in CDK5 while the conserved lysine in PAR was mutated to an arginine [48, 51]. 

Heterogeneous phosphorylation is often a problem when kinases are expressed in insect cells. Multiple approaches have been used to solve this problem. Proteins have been completely dephosphorylated by incubation with A protein phosphatase or alkaline phosphatase [38, 39, 56]. Ion exchange and isoelectric focusing chromatography have been used to separate proteins with multiple phosphorylation states. An y-aminophenyl ATP-sepharose column was used to separate different phosphory-lated states of human c-Src [34]. Alternatively, serine/threonine or tyrosine phosphorylation sites can be mutated to alanine or phenylalanine, respectively [42]. For tyrosine kinases with multiple autophosphorylation sites, the active site aspartic acid can be mutated to an asparagine, creating a kinase dead mutant [57]. 

The first step in the formation of urea from ammonia is its combination with bicarbonate to form carbamyl phosphate (Fig. 1). This contributes only one nitrogen atom to urea, the other being donated by aspartic acid in the third step of the pathway. A -Acetylglutamate is required as cofactor, and the presence of Mg is essential, ATP being converted to ADP in the process. The reaction is catalyzed by carbamyl phosphate synthetase (carbamate kinase EC 2.7.2.2). It has been shown that there are probably two forms of this enzyme, at least in rat liver. One is ammonia dependent, is primarily associated with mitochondria, and may be the enzyme responsible for the formation of carbamyl phosphate in the synthesis of urea. The other, which is glutamine dependent, is probably mainly extramitochondrial and may supply the carbamyl phosphate used... 

Pseudokinases are a protein family that constitute approximately 10% of the human kinome (for reviews on this topic, see Ref. 51-53). These proteins are characterized by the presence of a kinase-homology domain predicted to lack enzymatic activity due to the absence of at least one of the three conserved critical catalytic motifs (1) the Val-Ala-Ile-Lys (VAIK) motif in subdomain II, in which the side-chain of Lys interacts with the a and p phosphates of ATP (2) the His-Arg-Asp (HRD) motif in subdomain Ylb, in which the aspartic acid is the catalytic residue and (3) the Asp-Phe-Gly (DFG) motif in sub-domain VII, in which the carboxylic moiety of aspartic acid binds the Mg11 ion that coordinates the p and y phosphates of ATP. Owing to their lack of intrinsic phosphoryl-transfer catalytic activity, pseudokinase domain-containing... 

Serine 759 (702) is the main site of phosphorylation by MAP kinase (see Adam, Chapter 13, this volume), and phosphorylation at this site, or modification of serine to aspartic acid by site-directed mutagenesis, has a distinct effect TM-dependent inhibition is diminished and TM-dependent high-affinity actin binding is absent (Redwood et al, 1993 Childs et al., 1992). 

Figure 17-1 Universal regulation by protein phosphorylation. Protein phosphorylation requires the coordinated actions of protein kinases, which transfer a phosphoryl group to a target protein, and protein phosphatases, which remove it via hydrolysis. Phosphorylation of a target protein can change its biological activity in many ways including enzymatic activity, intracellular localization, and its ability to interact with other macromolecules such as DNA, RNA, and proteins. The most common amino acids which are phosphorylated in eukaryotic organisms are serine, threonine, and tyrosine. Phosphorylation on histidine with subsequent phosphoryl transfer to aspartic acid represents a coitunon modification in prokaryotic two-component signal transduction s)rstems (see Figure 17-15A).

Glover, R. T, Angiolieri, M., Kelly, S., Monaghan, D. T, Wang, J. Y, Smithgall, T. E., and Buller, A. L. (2000). Interaction of the A-methyl-D-aspartic acid receptor NR2D suhunit with the c-Abl tyrosine kinase./. Biol. Chem. 275, 12725-12729. 

Bypassing the pyruvate kinase step requires oxaloacetate. The oxaloacetate can come from either of two sources. First, various reactions can build up TCA cycle intermediates, among them oxaloacetate. For example, aspartic acid has the same carbon skeleton as oxaloacetate and ammonia can be removed by several means to yield oxaloacetate ... 

Woolf CJ, Thompson 8W (1991) The induction and maintenance of central sensitization is dependent on V-methyl-D-aspartic acid receptor activation implications for the treatment of postinjury pain hypersensitivity states. Pain 44 293-299 Wu ZZ, Guan BC, Li ZW, Yang Q, Liu CJ, Chen JG (2004) 8ustained potentiation by substance P of NMDA-activated current in rat primary sensory neurons. Brain Res 1010 117-126 Yamada K, Akasu T (1996) 8ubstance P suppresses GABAA receptor function via protein kinase C in primary sensory neurones of bullfrogs. J Physiol 496(Part 2) 439 49... 

The central nervous system of the ascidian tadpole larvae consist of 370 cells with PCNA proteins in the nuclei. An antisense oligonucleotide can inhibit the PCNA mRNA. Inhibition of PCNA resulted in deformed head development with cessation of DNA synthesis and nuclear DNA fragmentation resembling programmed cell death [1094]. The drosophila or mosquito dacapo is a Cip/Kip family cell cycle inhibitoiy protein of 261aa residues (cycline-dependent kinase inhibitory protein kinase inhibitory protein). The serine-threo/any aa/glutamate/aspartic acid... 

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