Study On The Properties And Structure Of Papain In Processing

Papain has an important application in food processing.In this paper,we were systematic studied the papain activity and structure by Folin phenol method,infrared spectra,SDS-PAGE electrophoresis,fluorescence spectra,ANS fluorescent probe,molecular dynamics method under the different temperature and pressure in the solution and powder condition respectively(called moist heat,dry heat,moist pressure and dry pressure).Furthermore,the hydrolysis mechanism of soybean protein isolate by papain was studied by molecular docking method(ZDOCK).The results showed that under the conditions of moist heat,papain had the highest activity at 50? and losed activity at 90?.The content of a-helix and fluorescence intensity was related to the activity of enzyme,but processing conditions had little effect on the molecular weight.Dry heat on the secondary structure was not obvious,but reduced the fluorescence intensity and hydrophobicity.Ultra-high pressure didn't significantly changed the enzyme activity and secondary structure,but reduced the fluorescence intensity and hydrophobicity.The molecular dynamics simulation was showed at 50 ? the difference of the structure of papain was a little,and the secondary structure was consistent with the experimental results.At 90 ? the difference of the structure was relatively larger,furthermore,it was found that the distance between the key amino acids increased and the structure became loose.The results of pressure show that under 500 MPa and 600 MPa there were a little effect on the structure,however,the radius of gyration became smaller.The molecular docking showed that papain had the interaction on the Leu174 and Lys175 of soy protein isolate A chain which caused hydrolysis.