Hydrolysis of Milk Proteins by Immobilized Streptomyces griseus Pronase

Open Access
Publisher Website
Google Scholar
Abstract
S. griseus pronase was coupled covalently to porous succinamidopropyl-glass beads with 1-ethyl-3-dimethylaminopropyl carbodiimide. The milk proteins, .alpha.-lactalbumin, RNase A, bovine serum albumin, .beta.-lactoglobulin, whole casein, commercial casein, .alpha.S1-casein, .beta.-casein and .kappa.-casein were recirculated through a packed-bed column of immobilized pronase. The rate and extent of hydrolysis of the milk proteins were estimated by a 2,4,6-trinitrobenzenesulfonic acid assay which measured liberated .alpha.-amino groups. Rates of hydrolysis varied from 0.46 .mu.mol .alpha.-amino groups released min-1 100 mg glass beads-1 for RNase A to 7.70 .mu.mol .alpha.-amino groups released min-1 100 mg glass beads-1 for a commercial preparation of casein while the extent of hydrolysis ranged from 5% .alpha.-amino groups released in 30 min for RNase A to 44% .alpha.-amino groups for .alpha.S1-casein in 15 min. Sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis visualized the rapid loss of major casein bands and degradation of the generated peptide fragments. Pseudo-1st order rate constant for N,N-dimethyl casein prepared by reductive alkylation was 5 .times. 10-2 min-1, while for casein, 7 .times. 10-2 min-1. Inclusion of 4 M urea with bovine serum albumin and simultaneous exposure to immobilized pronase gave a 2-fold increase in rate and extent of hydrolysis.

This publication has 27 references indexed in Scilit: