Regulation of alpha-amylase biosynthesis in Pichia burtonii B]

The synthesis of amylolytic enzymes by Pichia burtonii strain CBS 6141 requires the presence of etarch, maltose, and saccharose. Glucose exerts a strong repression which completely inhibited snzyme induction.     

Regulation of lysine biosynthesis in the leucine-dependent mutant of Micrococcus glutamicus]

The role of leucine in metabolism of Micrococcus glutamicus was examined in relation to the lysis synthesis by the homoserine- and leucine-dependent strains of M. glutamicus 106 and the homoserine-dependent strain of M. glutamicus 95. In addition to the growth function, leucine produced a controlling effect on the yield of the end product. In the presence of leucine the inhibitory effect of isoleucine on the lysine yield was reduced or reversed. The end effect depended on the leucine: isoleucine ratio. The mechanism of interaction of amino acid metabolites with respect to the lysine biosynthesis in both strains is discussed.     

The role of Mg2+-dependent phosphatidate phosphohydrolase in pulmonary glycerolipid biosynthesis

Rat lung microsomes washed with increasing concentrations of NaCl show a displacement of protein from microsomes to the wash supernatant. Among the proteins removed from the microsomal surface was the Mg2+-dependent phosphatidate phosphohydrolase, while the Mg2+-independent activity remained associated with the microsomes. The Mg2+-dependent activity could be quantitatively assayed in the wash supernatant. Microsomes washed with increasing concentrations of NaCl showed a progressive impairment in the synthesis of labelled neutral lipid and phosphatidylcholine from [14C]glycerol 3-phosphate with a concomitant increase in the labelling of phosphatidic acid. The impairment was sigmoidal and correlated highly with the decrease in Mg2+-dependent phosphatidate phosphohydrolase activity. When Mg2+-dependent phosphatidate phosphohydrolase from wash supernatant was incubated with microsomes previously washed with high salt concentrations, the labelling of neutral lipid and phosphatidylcholine was returned to control levels. Labelling of neutral lipids and phosphatidylcholine could be restored upon addition of a cytosolic Mg2+-dependent phosphatidate phosphohydrolase isolated by gel filtration. Mg2+-independent phosphatidate phosphohydrolase isolated from cytosol was incapable of restoring the labelling of neutral lipids and phosphatidylcholine. These findings confirm that the Mg2+-dependent phosphatidate phosphohydrolase of rat lung is involved in pulmonary glycerolipid biosynthesis. The role of the Mg2+-independent phosphatidate phosphohydrolase activity remains unknown.     

Regulation of extracellular acid phosphatase biosynthesis by culture conditions in entomopathogenic fungusMetarhizium anisopliae strain CQMa102

Metarhizium anisopliae is an imperfect entomopathogenic fungus. Once invading into its host,M. anisopliae needs to absorb basic nutrients such as phosphorus from the host haemolymph. A large number of phosphorylated compounds in haemolymph cannot be directly utilised by the fungal cell and must be hydrolysed into available form by phosphatase before ingested. Aims of this paper were to investigate optimum fermentation conditions for production of acid phosphatase and phosphatase isoenzymes byMetarhizium anisopliae. The optimum fermentation conditions were: glucose, 20 g/l; (NH₄)₂SO₄, 2 g/l; casein, 4 g/l; MgSO₄, 0.5 g; KCl, 0.5 g; microelement salt solution, 10 ml; inoculum size, 1×10⁷ spores per 100 ml medium; initial medium pH, 6.0. Under these conditions, the highest total acid phosphatase activity was 3.05 U/ml in 4 days at 27 °C and 160 rpm. Synthesis of the acid phosphatase was repressed by 0.01% inorganic phosphate in culture medium. The spectrum of isoenzymes produced byM. anisopliae varied depending on the phosphorus source employed in the culture. A specific isoform with pI 9.45 was induced by casein, and another isoform of pI 8.21 was induced by phytic acid and disodium phenyl phosphate.     

Regulation of extracellular acid phosphatase biosynthesis by phosphates in proteinase producing fungus Humicola lutea 120-5

The feasibility of using proteinase producing fungus Humicola lutea 120-5 as a source of extracellular acid phosphatase was investigated. To enhance the acid phosphatase yield and significantly reduce the proteolytic activity the composition of casein-glucose medium containing inorganic phosphate (Pi) was modified. The regulation of phosphatase formation was controlled by Pi. The repression influence of Pi on the synthesis of phosphatase was established. A reduction of Pi (KH(2)PO(4)) concentration from 1.0 to 0.01 g/l caused approximately 5-fold increase of the phosphatase (1200 U/I) and 3-fold decrease of the proteinase (10 U/ml). The omission of Pi from the medium in which the casein (phosphoprotein) was the sole phosphatase source resulted in higher phosphatase yield (2000 U/l) and lower proteolytic activity (7.5 U/ml). Different concentrations of glucose and casein were tested to obtain the optimal medium for maximal acid phosphatase production and minimal level of proteinase. The highest acid phosphatase activity of 2500 U/l and the least amount of acid proteinase (5.5 U/ml) were achieved in 72 h shake-flask culture using Pi-free medium containing glucose and casein in concentrations of 20 and 4 g/l, respectively. The ability of the fungus H. lutea 120-5 to dephosphorylate casein providing orthophosphate for cell growth was discussed.     

Regulation of tetracycline biosynthesis by controlling the growth of the producer]

Regulation of the rate growth of Act. aureofaciens in batch fermentation by maintaining the concentrations of phosphorus, ammonium nitrogen, glucose and pH values at the levels favourable for intensive growth at the beginning of the process and after accumulation of the biomass at the levels optimal for retarded growth of the organism resulted in significant prolongation of the period of intensive antibiotic production, i.e. intensification of the fermentation process. Microscopic investigation of the organism development under conditions of regulated fermentation revealed the presence of significant amounts of free peripheral highly basophilic hyphae for a prolonged period of time. The hyphae possessed a capacity for growth and intensive metabolism unlike the control culture which was liable to early autolysis.     

Regulation of ethylene biosynthesis in plants

Ethylene is one of the plant hormones that controls growth and development. There are many responses regulated via ethylene in response to exogenous stimuli. Research on ethylene biosynthesis and the signalling pathway enabled us to understand the mechanism of the regulation of these responses. Different temporal and spatial expression of genes encoding enzymes involved in ethylene biosynthesis is of great importance for the regulation of ethylene responses. Also, post-translational regulation of the enzymes seems to be a key regulatory mechanism for the control of their activity. Because of versatile regulation of its production, ethylene can control plant development at many levels.     

Regulation of the biosynthesis of hyaluronic acid. Role in the proliferation of fibroblasts]

The treatment of human skin fibroblasts with hyaluronidase stimulated the activity of hyaluronate synthase and the amount of hyaluronate secreted into the medium increased with the concentration of the enzyme and the time of the treatment. The maximal increase (about 3 fold) was independent of the type of glycosidic linkage cleaved, was inhibited neither by hyaluronate nor by oligosaccharides from hyaluronate and decreased in the late passage cultures. The increased hyaluronate synthesis was parallelled by 40% stimulation of the proliferation of fibroblasts up to 24th cell passage. The 10% stimulation of cell growth in late (36th passage) indicates a decrease in the ability of fibroblasts to respond to the degradation of the pericellular hyaluronate with in vitro ageing.     

Regulation of renal sulfoglycolipid biosynthesis

The in vitro activity of the renal galactolipid sulfotransferase and the level of sulfated glycolipids in the rat kidney have been correlated as a function of age. The galactolipid sulfotransferase was found to be greatly reduced in the young as compared with the adult animal. The relatively minor changes in the sulfated glycolipid content of the kidney with age suggests that an increase in sulfoglycolipid turnover occurs during growth. An inhibitory activity was detected in the homogenate supernate of the young animal capable of reducing the in vitro sulfotransferase activity of the adult. Assay of the human renal galactolipid sulfotransferase showed that this enzyme activity is deleted in samples of the blastematous form of Wilm's renal tumor. The results suggest that the rate of synthesis of renal sulfoglycolipids may prove a marker of renal development, perhaps by post translational regulation.