Characterization of a glutamyl aminopeptidase from Bacillus licheniformis NS115 = Bacillus licheniformis NS115가 생산하는 glutamyl aminopeptidase의 특성

Abstract

An extracellular glutamyl aminopeptidase (EC 3.4.11.7) producing bacterium was isolated from soil and identified as Bacillus licheniformis based on its morphological and physiological characteristics. The aminopeptidase was purified to homogeneity by ammonium sulfate precipitation, Phenyl Sepharose, Resource Q, and Superose 12 column chromatographies. The specific activity of the purified aminopeptidase was 9.2 unit/mg for glutamyl p-nitroanilide with 17.6 purification folds. The purified aminopeptidase had an estimated molecular mass of 64 kDa consists of two different subunits (42 kDa and 22 kDa), and its isoeletric point was 5.2 measured by isoelectric focusing. The optimum pH and temperature of the aminopeptidase were 8.0 and 55°C, respectively. The aminopeptidase was inhibited by EDTA and 1,10- phenanthroline, suggesting it be a metalloenzyme. Comparing with other aminopeptidase, the enzyme showed relatively high activity against peptide having glutamic acid as N-terminal.