Title
Two heat resistant endopeptidases from Pseudomonas species with destabilizing potential during milk storage
Author
Veronika Volk, Claudia Glück, Sebastian Leptihn, Jacob Ewert, Timo Stressler, Lutz Fischer
Year
2018
Journal
Journal of Agricultural and Food Chemistry
Abstract
In the current study, the extracellular endopeptidases from Pseudomonas lundensis and Pseudomonas proteolytica were investigated. The amino acid sequence identity between both endopeptidases is 68 %. Both endopeptidases were purified to homogeneity and partially characterized. They were classified as metallopeptidases with a maximum activity at pH 10.0 (P. lundensis) or 8.5 (P. proteolytica) at 35 °C. Both remained active in skim milk with 39.7 ± 2.4 % and 24.5 ± 3.3 %, respectively, of the initial enzyme activity after UHT processing (138 °C for 20 s), indicating the relevance for milk destabilization. The transition points in buffer were determined at 50 °C (P. lundensis) and 43 °C (P. proteolytica) using circular dichroism spectroscopy. The loss of the secondary structure at different temperatures was correlated with residual peptidase activities after heat treatment. The ability to destabilize UHT milk was proven by supplementation of skim milk with endopeptidase and storage for four weeks.
Instrument
J-715
Keywords
Circular dichroism, Secondary structure, Thermal stability, Protein folding, Food science, Biochemistry