Factors affecting the activity and stability of alkaline phosphatase in a marine pseudomonad

Constitutive production of aconitate isomerase by Pseudomonas sp. WU-0701 in relation to trans-aconitic acid assimilation

Aconitic acid, an unsaturated tricarboxylic acid, is used in the chemical industry as raw materials for organic synthesis, especially as a specific substrate for a flavoring agent. trans-Aconitic acid (tAA) is a trans-isomer of cis-aconitic acid and detected in some plants and bacteria. However, biosynthetic route and metabolism of tAA in relation to assimilation have been unknown. Aconitate isomerase (AI; EC 5.3.3.7) catalyzes the reversible isomerization between cis-aconitic acid and tAA. Pseudomonas sp. WU-0701 was isolated as a bacterium assimilating tAA as sole carbon source, and characterization and gene identification of AI were already reported. Here, we describe that Pseudomonas sp. WU-0701 exhibited growth in each synthetic medium containing glucose, citric acid, isocitric acid, or tAA as sole carbon source. AI was intracellularly detected all the time during the cultivation of the strain WU-0701 cells, irrespective of the carbon sources; AI activity was detected even in the glucose-grown cells. Through the subcellular fractionation experiments, AI was detected in the periplasmic fraction. This is the first report indicating that a bacterium belonging to the genus Pseudomonas is constitutive for the AI production.

A three step approach for the purification of alkaline phosphatase from non-pasteurized milk

In this study, a three step purification of alkaline phosphatase from non-pasteurized milk has been described. It included cream extraction, n-butanol treatment and acetone precipitation. Different parameters such as buffer concentration, temperature, pH, substrate concentration, acetone and n-butanol treatment were optimized to maximize the enzyme activity. The enzyme was fruitfully purified up to homogeneity from the milk, with percentage recovery and fold purification of 56.17 and 17.67 respectively. The kinetic parameters were determined to be 0.927 mM (Km) and 55.86 μM/min (Vmax), with specific activity of 11.31 U/mg. Other optimized parameters were estimated as a buffer concentration of 0.5 M with pH 9.0, temperature optima at 37 °C, with n-butanol and acetone concentration of 20 % (v/v) and 50 % (v/v) respectively. This approach provides a simple and effective method for the purification of alkaline phosphatase from non-pasteurized milk.

Biochemical and physiological properties of alkaline phosphatases in five isolates of marine bacteria

The alkaline phosphatase activities of five unique isolates of marine bacteria were found to be associated with the periplasmic space; however, the enzymes from these isolates differed with respect to their repressibility, the apparent number of isoenzymes, the necessity for Mg2 for activity, and the conditions required for their release. With three of the isolates, the enzyme was released when cells that had been washed in 0.5 M NaCl were suspended in sucrose; however, with the other two isolates, one required the additional presence of tris(hydroxymethyl)aminomethane and the other required the presence of lysozyme and ethylenediaminetetraacetic acid. In two isolates the activity was constitutive, in two it was partially repressed, and in one it was completely repressed by inorganic phosphate. The repression of activity was associated with corresponding changes of activity bands as seen by acrylamide gel electrophoresis.

Ultrastructure of cell envelopes of bacteria of the bovine rumen

Most of the bacteria found in rumen fluid samples taken from cows fed hay, or a concentrate diet, had cell walls of the gram-negative type. Most were intact, with only a small proportion of lysed cells, and many of the cells contained electron-translucent cytoplasmic deposits similar to the carbohydrate reserve material described in pure cultures of rumen organisms. All of the bacteria observed in these samples had an external "coat" layer outside the outer membrane when fixed in glutaraldehyde and osmium, stained with uranyl acetate and lead citrate, and examined as sectioned material. These coat layers varied from thin (ca. 8 nm) structures to very extensive fibrous systems, sometimes including concentric arrangements and radial fibers extending up to 1,200 nm from the cell. The thin-coat layers sometimes exhibited a rough periodicity. In all, 10 different types of coat layers were distinguishable on a morphological basis. It is proposed that these external coat layers have protective and adherence functions for the rumen bacteria in the environment.

Biochemical localization of alkaline phosphatase in the cell wall of a marine pseudomonad

The various layers of the cell envelope of marine pseudomonad B-16 (ATCC 19855) have been separated from the cells and assayed directly for alkaline phosphatase activity under conditions established previously to be optimum for maintenance of the activity of the enzyme. Under conditions known to lead to the release of the contents of the periplasmic space from the cells, over 90% of the alkaline phosphatase was released into the medium. Neither the loosely bound outer layer nor the outer double-track layer (cell wall membrane) showed significant activity. A small amount of the alkaline phosphatase activity of the cells remained associated with the mureinoplasts when the outer layers of the cell wall were removed. Upon treatment of the mureinoplasts with lysozyme, some alkaline phosphatase was released into the medium and some remained with the protoplasts formed. Cells washed and suspended in 0.5 M NaCl were lysed by treatment with 2% toluene, and 95% of the alkaline phosphatase in the cells was released into the medium. Cells washed and suspended in complete salts solution (0.3 M NaCl, 0.05 M MgSO(4), and 0.01 M KCl) or 0.05 M MgSO(4) appeared intact after treatment with toluene but lost 50 and 10%, respectively, of their alkaline phosphatase. The results suggest that the presence of Mg(2+) in the cell wall is necessary to prevent disruption of the cells by toluene and may also be required to prevent the release of alkaline phosphatase by toluene when disruption of the cells by toluene does not take place.