PubMed · 6216393
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J G Joshi. 1982. Phosphoglucomutase from yeast.. https://doi.org/10.1016/s0076-6879(82)89103-9
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A quantitative comparison was made on the fractionation of pepsin-digested horse antivenoms by ammonium sulfate (AS) fractional precipitation and ion-exchange chromatography on Q-Sepharose. In the precipitation process, pepsin digested horse anti-Naja kaouthia serum was precipitated by 30% saturated AS followed by 50% saturated AS. The recovery of antibody activity [as measured by an enzyme-linked immunosorbent assay (ELISA) against the cobra postsynaptic neurotoxin 3] from the 30-50% saturated AS precipitate was 53% with a 1.93-fold purification. For the chromatographic process, the behavior of the horse antitoxin antibody and its F(ab')2 fragments was first studied. The pepsin digested horse serum was then desalted on a Bio-gel P-2 column followed by chromatography on Q-Sepharose using a linear gradient (20 mM Tris-HCl, pH 8.0 containing 0.0 to 0.5 M NaCl) A peak containing primarily the F(ab')2 antibody could be obtained. This peak constituted 73% of the total antivenom activity with 2.08-fold purification. The total recovery of antibody activity by the chromatographic process was 90%. The yield of antibody activity was about 2-fold higher than that reported previously with other fractionation procedures. The implications of these results for the refining of horse therapeutic antivenoms are discussed.
Halophilic malate dehydrogenase is stable in a limited concentration range of MgCl2 or CaCl2. Thermal deactivation of the protein at low concentrations of these divalent salts is very different from that occurring at high concentrations. In low salt, stability always increases as the temperature is lowered. In high salt, stability shows bell-shaped behaviour as a function of temperature: increasing to a maximum at 4 degrees C, and subsequently decreasing as the temperature is lowered. This is in contrast to other salts, for which the deactivation behaviour depends on the salt type but not on its concentration. Cofactor addition or replacement of H2O by D2O modify only the deactivation at low MgCl2 or CaCl2 concentrations. A pH transition between pH 7 and pH 8, however, modified enzyme deactivation at both low and high MgCl2 or CaCl2 concentrations. The pH effect on stability was also observed in other salts. By comparing the effect of CaCl2, MgCl2, and NaCl, a strong correlation was found between the minimum salt concentration required for the stabilisation of halophilic malate dehydrogenase and the hydration of the cation.
The superoxide dismutase of Propionibacterium shermanii shows similar activity with iron and manganese bound at the active site of the protein. On the other hand, the iron form, in comparison to the manganese form, exhibits higher stability towards thermal- and pH-dependent inactivation. Upon inactivation the metal ions are released from the active site. Thus, in comparison to the manganese form, a higher stability of the iron-protein complex might be the triggering reason for this behavior.