Studies On Catalytic Mechanism And Stabilizer Of Acid Protease From Aspergillus Niger Sl2-111

Acid protease is a general call for any enzyme which can decompose protein under condition of acidity, Aspergillus niger and Aspergillus oryzae was the major mold producing acid protease in industry. In order to exploit the capacity of Aspergillus niger in molecular acting mechanism and conquer the problems in industry application , it is of more necessary to carry out this paper.In this study, the production conditions of three components of acid protease from Aspergillus niger SL2-111 were investigated. Major results were as follows:(1) Acid Protease was purified to elecrophoretic homogeneity by the steps of ammonium sulfate precipitation.DEAE-Sepharose Fast Flow column chromatography.Sephacryl S-200 column chromatography and high performance liquid chromatography.Its purity was checked to be about a single band by SDS-PAGE. the molecular weight was about 47 Kda, .The N-terminal partial sequence was SKGSAVTTPQ ,which indicated a high homology with other protease produced by aspergillus.(2) Acid protease was not affected by PCMB, Acetyl acetone, MA .. CDC modification,indicating that ε-amino group, arginine residues , Mercapto and carboxyl were non-essential to the enzyme activity. The enzyme activity was significantly decreased after NBS,N-AI and DTT modification,and was slightly decreased after BrAc modification.These results indicated that the histidineresidues.tryptophane residues,tyrosine residues and disulfides groups seemed to be essential to catalytic activity or located at the active site of acid protease. The otherness of Hydrolyze of Bovine haemoglobin ,Bovine serum albumin, Egg albumin and casein which casein was the most obvious Hydrolyzing , the result of dynamics was that the casine was the optimum substrate.