Secretory Expression, Purification, Characterization, and Application of an Aspergillus oryzae Prolyl Aminopeptidase in Bacillus subtilis.

cDNA coding a prolyl aminopeptidase (PAP) was cloned from Aspergillus oryzae and over expressed in Bacillus subtilis with a 6×His tag in N-terminus. The recombinant prolyl aminopeptidase was secreted to extracellular by adding 2 mM CaCl2 and 5% D-sorbitol in TB medium; the enzyme activity in fermented supernatant increased from 7.2 to 41.5 U mL-1. It has been purified 4.3-fold through Ni-chelating affinity chromatography with a recovery of 47.3%. The purified enzyme is stable below 50 °C and within pH 6-11, and with the highest activity at pH 7.5 and 50 °C. Several kinds of salt can activate enzyme activity in a certain concentration and the relative activity was 127.02% even when the concentration of NaCl reached 4.36 M. It cleaved N-terminal Pro residues from many peptides but shown different hydrolysis rates for various Pro-X dipeptides or peptides which are of different lengths. It combined with alkaline protease and leucine aminopeptidase to hydrolyze casein, many free amino acid especially proline and small peptide of hydrolysate increased significantly.

Over-expression of a proline specific aminopeptidase from Aspergillus oryzae JN-412 and its application in collagen degradation.

A strain that exhibited intracellular proline-specific aminopeptidase (PAP) activity was isolated from soy sauce koji and identified as Aspergillus oryzae JN-412. The gene coding PAP was cloned and efficiently expressed in Escherichia coli BL21 in a biologically active form. The highest specific activity reached 52.28 U mg(-1) at optimum cultivation conditions. The recombinant enzyme was purified 3.3-fold to homogeneity with a recovery of 36.7% from cell-free extract using Ni-affinity column chromatography. It appeared as a single protein band on SDS-PAGE with molecular mass of approximately 50 kDa. The purified enzyme exhibited the highest activity at 60 °C and pH 7.5. The enzyme activity was inhibited by PMSF and ions like Zn2+ and Cu2+. DTT, ß-mercaptoethanol, EDTA, and ions like Co2+, Mg2+, Mn2+, and Ca2+ had no influence on enzyme activity, whereas Ni2+ enhanced the enzyme activity. By using collagen as a substrate, the purified recombinant prolyl aminopeptidase contributed to the hydrolysis of collagen when used in combination with neutral protease, and free amino acids in collagen hydrolysates was significantly increased.

A thermo-stable lysine aminopeptidase from Pseudomonas aeruginosa: Isolation, purification, characterization, and sequence analysis.

Pseudomonas aeruginosa NJ-814, isolated from garden soil, produced an extracellular aminopeptidase that was purified using ammonium sulfate precipitation and ion exchange chromatography. The purity was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the Mr value of the enzyme was estimated to be 55 kDa. The purified enzyme shows maximum activity at pH 9.0 and 80 °C. It exhibits high thermo-stability. Half of the activity can remain after incubation at 80 °C for 119 min. It is stable within pH range of 7.5-10.5. It is strongly activated by Co(2+) and inhibited by Fe(2+) , Cu(2+) , Ni(2+) , Zn(2+) , and ethylene diamine tetraacetic acid (EDTA). The specificity of the enzyme was investigated. Within several aminoacyl-p-nitroanilines (AA-pNA), Lys-pNA is proven to be the optimal substrate. The Michaelis-Menten constant (Km ) of the enzyme for Lys-pNA and Leu-pNA were 2.32 and 9.41 mM, respectively. Peptide map fingerprinting shows that the sequence of the enzyme is highly similar to aminopeptidase Y from P. aeruginosa 18A. It can be speculated that this enzyme is a Zn(2+) -dependent enzyme and contains two zinc ions in its active site.

Purification and characterization of a urethanase from Penicillium variabile.

Urethanase produced by Penicillium variabile was purified through ultrasonication, concentration by polyethylene glycol 20,000, and Superdex G-200 gel filtration chromatography. The molecular weight of urethanase was determined to be around 96 kDa by gel filtration. The purified enzyme showed a single band in SDS-PAGE with the molecular weight of ~13.7 kDa, which suggests that the enzyme has a multimeric structure composed of the same subunits. Peptide map fingerprinting analysis was then carried out by MALDI/TOF-TOF MS. Within the known sequences in NCBI, glucosamine-6-phosphate deaminase and 6-phosphogluconate dehydrogenase get high score as compared with urethanase. Sequence analysis informs that N-terminal sequence of urethanase is GTNTADNDAA. The Minchaelis constant (Km) and maximum reaction rate (Vm) of urethanase are 27.2 mmol/L and 156.25 µmol/L min, respectively.

Isolation and characterization of urethanase from Penicillium variabile and its application to reduce ethyl carbamate contamination in Chinese rice wine.

A strain with urethanase activity was isolated from mouse gastrointestine. By combination of morphological characterization of the colony, hyphae, and spore and the sequence analysis of its rDNA ITS, the strain was determined as Penicillium variabile and named as P. variabile JN-A525. The enzymatic properties of urethanase from P. variabile JN-A525 were further studied. The optimum temperature and pH value of urethanase are of 50 °C and 6.0, respectively. The enzyme maintains stability when the temperature is below 50 °C and the pH is in the range of 7.0-10.0. The enzyme also exhibits ethanol tolerance. It can remove ethyl carbamate from Chinese rice wine without the change of flavor substances in the wine.

Purification of a novel pepsin inhibitor from Coriolus versicolor and its biochemical properties.

A novel pepsin inhibitor was isolated from Coriolus versicolor. The purification was carried out by a 2-step ultrafiltration followed by DEAE-52 and Mono Q ion-exchange chromatography. SDS-PAGE and gel filtration chromatography analysis showed that the isolated inhibitor was a 22.3 kDa protein with a single subunit. Heat stability of this inhibitor was estimated and only 7% of its inhibitory activity lost after treatment at 98 °C. The inhibitor was more specific against pepsin than several other proteases. The dissociation constant (K(i)) and concentration required for 50% pepsin inhibition (IC50) were 5.84 × 10(-5) M and 26.26 µg/mL, respectively. Apparent decrease of α-helix and increase of random coil were observed in the circular dichroism spectra of pepsin when an equimolar amount of the inhibitor was added. The inhibition mechanism of this inhibitor differs from the reported aspartic protease inhibitors, according to the secondary structure and the kinetic studies of this inhibitor.