Kinetics Of Enzyme Production Research Articles

Biosynthesis of Escherichia coli aspartate transcarbamylase : I. Parameters of gene expression and sequential biosynthesis of the subunits

When Escherichia coli is derepressed for the biosynthesis of aspartate transcarbamylase, a balanced production of catalytic and regulatory subunits is observed. Upon repression, the biosynthesis of catalytic chains stops before that of regulatory chains. These results suggest that the biosynthesis of the two kinds of chains is directed by a polycistronic messenger RNA. The parameters of expression of the corresponding genes were determined: lag-times for derepression and repression, kinetics of enzyme production, half-life of the specific messenger RNA. From these data, the periodicity of transcription and the average number of ribosomes translating each molecule of messenger RNA were calculated. The results are in agreement with those reported for β-galactosidase and tryptophan synthetase biosynthesis.

The stability and cell content of penicillinase messenger RNA in Bacillus licheniformis.

SUMMARY: The stability of penicillinase messenger RNA has been assessed from the kinetics of enzyme production after inhibition of RNA synthesis with actinomycin or rifampicin. An average messenger half-life of 4.7 min. is indicated, both for induced Bacillus licheniformis 749, and the constitutive mutant 749/c. Although this value is twice that estimated for average total m-RNA by similar techniques, there is no indication of a ‘long-lived messenger’ as previously implicated in other reports. An attempt was made to estimate the content of penicillinase messenger from data on the level of penicillinase made per bacterium, the polysome size, the messenger half-life and the total level of unstable RNA per bacterium. It is suggested that at the maximum induced rate of enzyme formation there are approximately 110 penicillinase messengers per bacterium, and in the constitutive about twice this number.