TAILIEUCHUNG - Báo cáo khoa học: Alanine aminotransferase of Trypanosoma brucei – a key role in proline metabolism in procyclic life forms

African trypanosomes possess high levels of alanine aminotransferase (EC ), although the function of their activity remains enigmatic, espe-cially in slender bloodstream forms where the metabolism of ketoacids does not occur. Therefore, the gene for alanine aminotransferase enzyme inTry-panosoma brucei(TbAAT) was characterized and its function assessed using a combination of RNA interference and gene knockout approaches. | ỊFEBS Journal Alanine aminotransferase of Trypanosoma brucei - a key role in proline metabolism in procyclic life forms Diana Spitznagel1 Charles Ebikeme2 Marc Biran2 Nóirín Nic a Bhaird1 Frederic Bringaud2 Gary T. M. Henehan3 and Derek P. Nólan1 1 Schoolof Biochemistry and Immunology Trinity College Dublin Ireland 2 Centre de Resonance Magnetique des Systemes Biologiques RMSB UMR 5536 CNRS Universite Victor Segalen Bordeaux 2 Bordeaux France 3 Schoolof Food Science and EnvironmentalHealth Dublin Institute of Technology Ireland Keywords alanine aminotransferase proline metabolism Trypanosoma brucei Correspondence D. P. Nolan School of Biochemistry and Immunology Trinity College Dublin Dublin 2 Ireland Fax 353 1 6772400 Tel 353 1 8962455 E-mail denolan@ Received 3 July 2009 revised 1 October 2009 accepted 12 October 2009 doi African trypanosomes possess high levels of alanine aminotransferase EC although the function of their activity remains enigmatic especially in slender bloodstream forms where the metabolism of ketoacids does not occur. Therefore the gene for alanine aminotransferase enzyme in Trypanosoma brucei TbAAT was characterized and its function assessed using a combination of RNA interference and gene knockout approaches. Surprisingly as much as 95 or more of the activity appears to be unnecessary for growth of either bloodstream or procyclic forms respiring on glucose. A combination of RNA interference and NMR spectroscopy revealed an important role for the activity in procyclic forms respiring on proline. Under these conditions the major end product of proline metabolism is alanine and a reduction in TbAAT activity led to a proportionate decrease in the amount of alanine excreted along with an increase in the doubling time of the cells. These results provide evidence of a role for alanine aminotransferase in the metabolism of proline in African trypanosomes by linking glutamate produced by the initial .

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