Portal de Periódicos da CAPES

Incorporation versus biosynthesis of leucine: implications for measuring rates of protein synthesis and biomass production by bacteria in marine systems

1986; Inter-Research; Volume: 32; Linguagem: Inglês

10.3354/meps032047

1616-1599

DL Kirchman, SY Newell, RE Hodson,

Metabolomics and Mass Spectrometry Studies

Rates of leucine lncorporahon have been suggested recently to be useful for estunating rates of protein synthesis and biomass product~on by bactena In natural water samples We examined 2 potential problems wlth this approach de novo synthesis of leucine and lntracellular protein turnover Rates of leucine and methionine biosynthesis were e s t ~m a t e d from the incorporation of '4C-pyruvate and 35S0,', respectively Leucine inhibited '4C-pyruvate and 'H-glucose incorporahon and methionine inhibited "SO, lncorporation However rates of biosynthesis of leucine and lnethionine were still much higher than the maximum rate of exogenous amlno acld Incorporation This problem can be surmounted with emplncally determined conversion factors which relate rates of leucine incorporation to rates of proteln synthesis or biomass production The ratio of the emplncally determined factor to the theoretical factor is similar to the ratio of the rate of biosynthesis to the incorporation rate of exogenous leuclne The rate of intracellular proteln turnover as determined by the pulse-chase approach was large compared wlth net protein synthesis ~n only 1 out of 5 expcnments Leuclne lncorporation rates are at least an underestimate of rates of protein synthesis and In some environments may prove to b e a useful measure of bacterial biomass production Our results also Indicate that the supply of dissolved amino acids may affect the uptake and minerahzatlon of other dissolved compounds vla regulation of amino acid uptake and biosynthesls D Inter-ResearchIPrinted in F. R. Germany