Enzymatic characterization of a soluble aggregate induced by N-terminal extension to a lipolytic enzyme

•Unusual enzymatic properties of a soluble aggregate with lipolytic activity are shown.•A catalytic domain of the enzyme was extended with 27 amino acids at the N-terminus.•The new lipolytic enzyme was expressed as highly soluble aggregate in E. coli.•Enzyme activity increased to that of the monomer at elevated temperature.•The aggregate was dissociated at elevated temperatures resulting in activation. A self-assembling peptide (27PEP) was isolated from an open reading frame (ORF). The ORF consisted of an unknown functional domain and a catalytic (lipolytic and phospholipolytic) domain (MPlaG) on metagenomic fosmid clone. This extension of 27 amino acids prior to the N-terminus of the catalytic domain (27PEP-MPlaG), starting at Met261, produced an aggregate of high molecular weight (> 700 kDa). Compared with MPlaG, 27PEP-MPlaG showed the same temperature and pH effect for maximum activity but was stable in the presence of inhibitors such as EDTA and PMSF. The 27PEP-MPlaG exhibited lower specific activity than that of MPlaG, but when pre-incubated for 30 min at temperatures between 4 and 100 °C, its activity increased at temperatures greater than 40 °C under alkaline conditions and eventually reached the specific activity level of MPlaG at 60 °C. We experimentally determined that the aggregate caused by 27PEP was dissociated at elevated temperatures resulting in an active catalytic monomer. The 27PEP-indued aggregation may be attractive as application tool for improving or engineering of biocatalysts and biomaterials.