RESUMEN
Streptococcus bovis has been found to contain two distinct aspartokinases that can be separated by gel filtration chromatography. One of these isozymes elutes on Sephadex G-200 gel filtration at a molecular weight greater than 250,000. The molecular weight of the other isozyme is approximately 125,000. The earlier peak of aspartokinase activity is slightly inhibited by meso-diaminopimelate, while the second peak is sensitive to inhibition by lysine. The latter aspartokinase is not formed when the organism is grown in a medium containing more than 1 mM lysine. The level of lysine-sensitive aspartokinase is decreased during the growth cycle, whereas diaminopimelate-sensitive activity is little affected by the growth conditions. The regulatory properties of the two aspartokinases suggest that they may play different physiological roles.
Asunto(s)
Aspartato Quinasa/metabolismo , Isoenzimas/metabolismo , Streptococcus bovis/enzimología , Aminoácidos/farmacología , Aspartato Quinasa/antagonistas & inhibidores , Aspartato Quinasa/aislamiento & purificación , Represión Enzimática , Isoenzimas/antagonistas & inhibidores , Isoenzimas/aislamiento & purificación , Lisina/farmacología , Streptococcus bovis/crecimiento & desarrolloRESUMEN
Some Bacillus subtilis mutants with different levels of homoserine dehydrogenase were described. Strains that do not accumulate methionine have a high homoserine dehydrogenase activity. Low activity was detected in mutants where cell growth was completely inhibited by 0.7 mmol/L methionine. A low concentration of dimethyl sulfoxide had a stimulatory effect on lysine production by the methionine-sensitive mutant of Bacillus subtilis.
