title: Isolation and characterization of heat stable proteinases from Pseudomonas isolate AFT 21.
abstract: Pseudomonas strain AFT 21 produced three heat stable extracellular proteinases in milk and nutrient broth at 7 or 21 degrees C, but the proportions depended on medium and cultivation temperature. The three proteinases were EDTA- and o-phenanthroline-sensitive metalloenzymes and were not inhibited by N-ethylmaleimide or phosphoramidon. Proteinases I and II showed maximum activity at pH 7-7.5 and proteinase III at pH 8.5. All three enzymes showed maximum activity at 45-47.5 degrees C, but had relatively high (19-27% of maximum) activity at 4 degrees C. They were unstable at 55 degrees C in phosphate buffer, pH 6.6, or synthetic milk ultrafiltrate (SMUF) containing 12 mmol Ca2+, but were stabilized by short preheating at 100 degrees C. They were extremely heat stable in both phosphate buffer and SMUF, pH 6.6, at 70-150 degrees C. Their D-values at 140 degrees C were 69, 54 and 80 s respectively. The Z-values for Pseudomonas AFT 21 proteinase III in phosphate buffer and SMUF were 29.7 and 30.3 degrees C respectively; the corresponding activation energies for inactivation were 8.7 x 10(4) J mol-1 and 9.2 X 10(4) J mol-1.
mesh_terms: D000818:Animals; D002417:Cattle; D004355:Drug Stability; D010450:Endopeptidases / Q000302:isolation & purification* / Q000494:pharmacology; D005260:Female; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000201:enzymology / Q000382:microbiology; D008970:Molecular Weight; D011480:Protease Inhibitors; D011549:Pseudomonas / Q000201:enzymology*; D013696:Temperature
chemical_list: D011480:Protease Inhibitors; D010450:Endopeptidases