Stabilization of a psychrotrophic Pseudomonas protease by calcium against thermal inactivation in milk at ultrahigh temperature.
The heat-stable extracellular protease of Pseudomonas sp. (isolate MC60) was investigated. Heat resistance of the enzyme in milk at sterilization temperature was dependent on the presence of Ca2+. The half-life of the enzyme at ultrahigh temperature (149 C) in skim milk or milk-salts buffer with Ca2+ was approximately 7.0 s. Treatment of milk with chelators completely removed the heatstabilizing effect of milk. The enzyme was partially purified by ammonium sulfate precipitation and column chromatography on Sephadex G-100. At 21 C the enzyme retained greater than 85% activity after exposure to pH values between 5 and 10. Enzyme activity was reduced by metal chelating agents. Both Ca2+ and Zn2+ were required for optimal enzyme activity. Molecular weight was estimated at 48,000 by gel filtration.
D000180:Acrylic Resins / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D005516:Food Microbiology; D005519:Food Preservation; D006207:Half-Life; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008892:Milk; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000378:metabolism*; D010618:Phenanthrolines / Q000494:pharmacology; D011549:Pseudomonas / Q000201:enzymology*; D013242:Sterilization
D000180:Acrylic Resins; D002614:Chelating Agents; D010618:Phenanthrolines; D004492:Edetic Acid; D010447:Peptide Hydrolases; D002118:Calcium