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oai:riuma.uma.es:10630/368492026-03-13T07:54:48Zcom_10630_2254col_10630_37953

00925njm 22002777a 4500 dc Montero, Fernando author Baglietto-Vargas, David author Moreno-González, Inés author López-Téllez, Juan Félix author Cuesta Muñoz, Antonio L. author Gutiérrez-Pérez, Antonia author Aledo-Ramos, Juan Carlos author 2007 Glutamatergic signalling plays an important role in the coordination of hormone secretion from the endocrine pancreas. Thus, glutamate production must be a process exquisitely regulated to ensure a proper transmitter function. Recently we have reported that the endocrine pancreas co-expresses two isoforms of the protein glutaminase (GA), denoted as kidney-type (KGA) and liver-type (LGA). However, how GA activity, and therefore glutamate production, is regulated in the islets represents a critical issue that remains unresolved. Since the purification of these enzymes from rat islets is a daunting task, in order to characterize each isoform we have taken advantage of the spatial segregation of these isoenzymes in pancreas. To assist us with this goal, we have developed a new procedure that enables us to assay GA activity in situ. The assay is highly specific for GA as indicated by its dependence on glutamine and orthophosphate. Surprisingly, LGA, which is abundantly expressed by β-cells, did not show detectable activity under the assay conditions. All the GA activity detected in pancreatic islets was attributed to KGA and was confined to the mantle of the islets. Double labelling analyses strongly suggested that α-cells should be regarded as the site of glutamate production in the endocrine pancreas. Montero F, Baglietto-Vargas D, Moreno-González I, López-Tellez JF, Cuesta-Munoz AL, Gutiérrez A, Aledo JC. Glutaminase activity is confined to the mantle of the islets of Langerhans. Biochimie. 2007 Nov;89(11):1366-71. doi: 10.1016/j.biochi.2007.05.008. Epub 2007 Jun 2. PMID: 17614191. https://hdl.handle.net/10630/36849 10.1016/j.biochi.2007.05.008 Ácido glutámico Glutaminase activity is confined to the mantle of the islets of Langerhans.