Citrulline identification

Other PTMs may involve changes in the chemical nature of amino acids (e.g., citrullination or deimination). Because many of these modifications result in mass changes that are measurable by MS, they are amenable to detection by MS-based approaches. A number of emerging MS-based strategies allow the identification of PTMs. Several MS-based methods to determine the types and sites of protein phosphorylation and ubiquitination have been developed. Phosphorylation occurs mainly on serine, threonine, and tyrosine residues at a frequency ratio of 1800 200 1 in vertebrates.70 Although the phosphorylation of tyrosine residues occurs less frequently in the proteome, it has been extensively studied. 

It presently became clear that ammonia, carbon dioxide, and ATP were forming an active intermediate which condensed with ornithine to give citrulline. The clue to its identification came from Lipmann s laboratory in 1955 (Jones, Spector, and Lipmann). Lipmann had been... 

Diagnosis is based upon hyperammonaemia, which is detectable either spontaneously or after the oral intake of proteins - or, most obviously, following intravenous infusion of amino acids. The respective amino acids are increased in the serum prior to the disturbed metabolic reaction. Argininosuccinate is only detectable in the urine. A striking feature in these patients is their thin, brittle hair. With defective ornithine transcarbamylase, there is an increase in orotic acid, uridine and uric acid in the urine, while the respective citrulline concentration is decreased. The determination of OTC activity in liver tissue verifies the diagnosis and facilitates a genomic analysis. (172) The allopurinol test can be applied for the identification of heterozygosity (or the mild form of OTC deficiency). The liver shows steatosis, portal inflammation and portal fibrosis. 

In his 1954 compilation of smoke components, Kosak (2170) listed no amide identified to that date. In their 1959 review of tobacco and tobacco smoke components, Johnstone and Plimmer (1971) described the identification of asparagine and glutamine in tobacco and glutamine and nicotinamide in tobacco smoke. The latter were identified in smoke by Buyske et al. (562). In its 1963 monograph on tobacco and smoke components, Philip Morris (2939) listed the amides, asparagine, glutamine, citrulline, and nicotinamide, as tobacco components but only glutamine and nicotinamide as smoke components. 

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