Autolysis of the Proteinase from Pseudomonas fluorescens

¹ Laboratory of Dairy Science, Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Sapporo 060-8589, Japan
² Bioscience and Chemistry Division; Hokkaido National Industrial Research Institute, 2-17-2-1 Tsukisamu-higashi, Toyohira-ku, Sapporo 062-8517, Japan

The gene encoding the proteinase from Pseudomonas fluorescens was cloned and sequenced in an effort to identify the cleavage sites involved in its autolysis at 50°C. A single open reading frame consisting of 1449 nucleotides, encoding a protein of 482 amino acids, was found. Analysis of the N-terminal amino acid sequence of the purified proteinase indicated the presence of a prosequence consisting of 13 amino acid residues. The molecular weight of the mature protein was calculated as 48,900 based on the deduced amino acid sequence, which was consistent with that of the purified proteinase as determined by sodium dodecylsulfate-PAGE. Greater than 90% loss of proteolytic activity was observed upon heating at 50°C for 2 min compared with the unheated enzyme. Incubation of the proteinase at 50°C led to disappearance of the intact enzyme, as shown by sodium dodecyl sulfate-PAGE, whereas it was stable in the presence of the protease inhibitor o-phenanthroline. Autolytic fragments were fractionated by reverse-phase HPLC and subjected to N-termal amino acid sequence analysis in an effort to determine the cleavage sites. The cleavage profile was not definitive; however, amino acid residues with small side chain groups, such as glycine or alanine, were frequently found adjacent to the cleavage sites.

Key Words: Pseudomonas fluorescens • proteinase • autolysis • proteinase gene

Submitted on February 8, 1999
Accepted on June 1, 1999