External factors involved in the regulation of an extracellular proteinase synthesis in Bacillus megaterium

Summary A mathematical model was formulated to describe the kinetics and stoichiometry of growth and proteinase production in Bacillus megaterium. Synthesis of the extracellular proteinase in a batch culture is repressed by amino acids. The specific rate of formation of the enzyme (r _E) can be described by the formula {ie373-1}, where k ₂ and k ₃ stand for the non-repressible and repressible part of enzyme synthesis respectively, k _{S 2} is a repression coefficient and S ₂ indicates the concentration of amono acids; the values of k ₂ and k _{S 2} depend on the composition of the mixture of amino acids. Even in a high concentration, a single amino acid is less effective than a mixture of amino acids. The dependence of the proteinase repression on the concentration of an external amino acid (leucine) follows the same course as its rate of incorporation into proteins, approaching saturation at concentrations higher than 50 M (half saturation approximately 10 M). However, the total uptake of leucine did not exhibit any saturation even at 500 M external concentration.Symbols X biomass concentration, g/l - E proteinase concentration, unit/l - t time, h - S ₁ concentration of glucose, g/l - S ₂ concentration of amino acids, g/l - specific growth rate, l/h - rE specific rate of enzyme production, unit/g/h - k ₁ growth kinetic constant, l/h - k ₂ product formation kinetic constant (for non-repressible part of enzyme synthesis), unit/g - k ₃ product formation kinetic constant (for repressible portion of enzyme synthesis), unit/g - k _{S 1} saturation constant, g/l - k _{S 2} repression coefficient for a certain amino acid or amino acids mixture, g/l     

Influence of leaf age on photosynthesis, enzyme activity, and metabolite levels in wheat

The rate of photosynthesis under high light (1000 micromole quanta per square meter per second) and at 25°C was measured during development of the third leaf on wheat plants and compared with the activity of several photosynthetic enzymes and the level of metabolites. The rate of photosynthesis reached a maximum the 7th day after leaf emergence and declined thereafter. There was a high and significant correlation between the rate of photosynthesis per leaf area and the activities of the enzymes ribulose 5-phosphate kinase (r = 0.91), ribulose 1,5-bisphosphate (RuBP) carboxylase (r = 0.94), 3-phosphoglycerate (PGA) kinase (r = 0.82), and fructose 1,6-bisphosphatase (r = 0.80) per leaf area. There was not a significant correlation of photosynthesis rate with chlorophyll content. The rate of photosynthesis was strongly correlated with the level of PGA (r = 0.85) and inversely correlated with the level of triose phosphate (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate) (r = 0.92). RuBP levels did not change much during leaf development; therefore photosynthesis rate was not correlated with the level of RuBP. The rate of photosynthesis was at a maximum when the ratio of PGA/triose phosphate was high, and when the ratio of RuBP/PGA was low. Although several enzymes change in parallel with leaf development, the metabolite changes suggest the greatest degree of control may be through RuBP carboxylase. The sucrose content of the leaf was highest under high rates of photosynthesis. There was no evidence that later in leaf development, photosynthesis (measured under high light and at 25°C) was limited by utilization of photosynthate.     

Purification and properties of a novel Ca2+-binding protein (10.5 kDa) from Ehrlich-ascites-tumour cells.

A novel Ca2+-binding protein (CaBP) was identified in Ehrlich-ascites-tumour cells and purified to homogeneity. The molecular mass of this protein is about 10.5 kDa as estimated by polyacrylamide-gel electrophoresis in the presence of SDS. CaBP has two Ca2+-binding sites that bind Ca2+ with a dissociation constant of about 3 x 10(-6)M. Ca2+ binding to CaBP decreases its electrophoretic mobility in urea/polyacrylamide gels, changes its u.v. spectrum, increases the intrinsic tyrosine fluorescence intensity and strengthens hydrophobic interaction with the phenyl-Sepharose matrix.     

Antimicrobial effects of some mono- and bishydrazones

Antibacterial, antifungal and antiprotozoal effects of nine mono- and bishydrazones of glycolaldehyde, glyoxal, methoxyacetaldehyde and glutaraldehyde were studied using eight model organisms. It was found that bishydrazones are much more efficient antimicrobial agents than monohydrazones in the case of all model microorganisms.     

Laser Doppler anemometer measurements of pulsatile flow in a model carotid bifurcation

Hemodynamics at the human carotid bifurcation is important to the understanding of atherosclerotic plaque initiation and progression as well as to the diagnosis of clinically important disease. Laser Doppler anemometry was performed in a large scale model of an average human carotid. Pulsatile waveforms and physiologic flow divisions were incorporated. Disturbance levels and shear stresses were computed from ensemble averages of the velocity waveform measurements. Flow in the common carotid was laminar and symmetric. Flow patterns in the sinus, however, were complex and varied considerably during the cycle. Strong helical patterns and outer wall flow separation waxed and waned during each systole. The changing flow patterns resulted in an oscillatory shear stress at the outer wall ranging from -13 to 9 dyn cm-2 during systole with a time-averaged mean of only -0.5 dyn cm-2. This contrasts markedly with an inner wall shear stress range of 17-50, (mean 26) dyn cm-2. The region of transient separation was confined to the carotid sinus outer wall with no reverse velocities detected in the distal internal carotid. Notable disturbance velocities were also time-dependent, occurring only during the deceleration phase of systole and the beginning of diastole. The present pulsatile flow studies have aided in identifying hemodynamic conditions which correlate with early intimal thickening and predict the physiologic level of flow disturbances in the bulb of undiseased internal carotid arteries.     

玉米酯酶同工酶和过氧化物酶同工酶的分子量研究

本试验利用聚丙烯酰胺凝胶梯度电泳分步染色法直接对玉米苗期酯酶同工酶和过氧化物酶同工酶各酶带的分子量进行了比较测定。酯酶同工酶 E_1、E_2、E_3~F、E_3~S、a、b、c 各酶带的分子量分别为<20000,35200、33000、38500、29900、28500、34000道尔顿过氧化物酶同工酶 PX_4~F和 PX_4~S酶带的分子量分别为131000和149000道尔顿。根据酶带在均匀胶和梯度胶中的位置变化对各酶带的生化性质作了初步分析,发现 E_3~F和 E_3~S、PX_4~F 和 PX_4~S 在迁移率上的差异主要是分子量的差异。本文为同工酶的分子量测定提供了一个简便的方法。     

山药化学成分的研究

从胡椒科植物山蒟中分得两个新木脂素类成分(Ia)和(Ⅱ),以及巴豆环氧素(Crorepoxide)(Ⅲ)和β-谷甾醇(Ⅳ)。经光谱分析及化学鉴定,(Ia)、(Ⅱ)为新结构,分别命名为山蒟素 B(hancinone)、山蒟素 C(hancinone C)。