Mechanisms of heat inactivation of a proteinase from Pseudomonas fluorescens biotype I

• Published in: Journal of dairy research 1987-02, Vol.54 (1), p.51-60
• Main Authors: Diermayr, Peter, Kroll, Stefan, Klostermeyer, Henning
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; denaturation; Endopeptidases; Food industries; Fundamental and applied biological sciences. Psychology; heat treatment; Hot Temperature; inactivation; milk; Milk and cheese industries. Ice creams; Original Articles; Protein Denaturation; proteinases; Pseudomonas fluorescens; Pseudomonas fluorescens - enzymology
• ISSN: 0022-0299; 1469-7629
• DOI: 10.1017/S002202990002519X

Heat inactivation of a metalloproteinase, isolated from Pseudomonas fluorescens biotype I strain 112, was investigated in the temperature ranges 50–60 °C and 90–140 °C. At 90 °C the denaturation of the enzyme followed first-order kinetics with a decimal reduction time of 110 min and a velocity constant K of 3·5 × 10−4 s−1. Activation energy Ea was 100 kJ/mol for this temperature range. In the 50–60 °C region the proteinase was inactivated by autolysis, as shown by electrophoresis and gel filtration. At 55 °C the decimal reduction time was ∼ 22 s, at 57 °C it was 8 s. Rapid inactivation at 55 °C was only possible if the enzyme was heated from lower temperatures, but not if cooled down from 90 °C. This is due to a conformational change of the protein at this temperature. A model for the description of heat inactivation in the two temperature ranges is proposed.