6-2 |
Bioactive substances from marine sources with a case study on protamine |
T. A. GILL1, R. Potter, and D. A. Pink1. (1) Dept. of Food Science & Technology, Dalhousie Univ., 1360 Barrington St., Bldg. D-401, PO Box 1000, Halifax, NS B3J 2X4, Canada Protamine is a cationic peptide derived from herring or salmon milt, and has been used for decades as a slow release carrier for injectable insulin as well as reversing the blood thinning properties of heparin during certain surgical procedures. It is the highest cationic (66% arginine on a molar basis), naturally occurring CAP studied to date. Protamine is heat resistant and able to withstand steam sterilization without any appreciable loss in antimicrobial activity. It kills susceptible bacteria through electrostatic attraction and subsequent lysis of the cell envelope. Our work has shown, however, that in some artificial culture media and foods, protamine may bind to and precipitate constituent proteins. This phenomenon may severely restrict it’s application to many foods. Also, the antibacterial efficacy of protamine may be reduced by bacterial proteolysis or from endogenous proteases within the food matrix. The present study was performed to gain knowledge of protamine’s efficacy in food applications. The surface charge of protamine sulfate was reduced by random blocking 10-71% of the positively-charged guanido groups of the arginine residues using 1,2-cyclohexanedione. Each of the modified protamines was tested for its inhibitory properties against a wide variety of food borne organisms. In real food systems, 10 and 20% modification led to greatly improved antibacterial efficacy. It would appear that the antibacterial effects of protamine are more dependent on competitive non-specific electrostatic interactions of this cationic peptide with food components than upon the bacterial envelope per se. Blocking the guanido groups of protamine with cyclohexanedione increased surface hydrophobicity but did not reduce its susceptibility to proteolysis by trypsin.
Session 6, Marine biotechnology
|