The derepression of enzymes of de novo pyrimidine biosynthesis pathway in Brevibacterium ammoniagenes producing uridine-5-monophosphate and uracil.

A mutant of Brevibacterium ammoniagenes producing large quantities of UMP and uracil is described. The mutations render bacteria braditrophic for arginine, sensitive to adenine, resistant to rifampicin and pyrimidine analogues 5-fluorouracil, 5-fluorouridine, azauracil and thiouracil. The activities of enzymes involved in the UMP biosynthesis, i.

A pleiotropic mutation affecting purine metabolism in Bacillus subtilis.

A pleiotropic mutation (cpm) which is localized in the vicinity of the spoOA gene is described in Bacillus subtilis. The mutation inhibits spore formation, rendering bacteria auxotrophic for adenine and tyrosine, enhances sensitivity to antibiotics, decreases cell motility, inhibits the ability to grow on pentoses and to maintain bacteriophage multiplication, induces severalfold the activities of alkaline proteinase and alpha-amylase. At the same time, the cpm mutant starts to excrete inosine into the growth medium.

[Glucose catabolite repression of glucoamylase biosynthesis by the yeast Endomycopsis fibuligera].

The effect of glucose, sucrose, fructose, maltose, alpha-methyl glucoside, glycerol, nonmetabolizing glucose analog--2-deoxy-D-glucose, and cyclic 3',5'-adenosine monophosphate (cAMP) on the glucoamylase biosynthesis by the yeast Endomycopsis fibuligera 20-9 was investigated. The sugars tested induced repression of the enzyme synthesis. The repressive effect of glucose, sucrose and maltose was reversed partially or completely by cAMP.

Involvement of the Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system in regulation of transcription of catabolic genes.

Synthesis of catabolite-sensitive enzymes is repressed in mutants defective in the general proteins (enzyme I and HPr) of the Escherichia coli phosphoenolpyruvate-dependent phosphotransferase system (ptsI and ptsH mutations). To elucidate the mechanism of this phenomenon we constructed isogenic strains carrying pts mutations as well as different lesions of regulation of the lac operon or mutations affecting adenylate cyclase activity (cya mutation) and synthesis of cyclic AMP-receptor protein (crp mutation) Measurements of the differential rate of beta-galactosidase synthesis in these strains showed that the repressive effect of pts mutations was revealed in lac+, lacI, lacOc and cya bacteria, but it was lost in lacP and crp strains. It was concluded that mutational damage to the general components of the phosphoenolpyruvate-dependent phosphotransferase system diminishes activity of the lac promoter.