30C-16 |
Is phaseolin resistant to pepsin in vitro proteolysis? |
S. K. SATHE and M. Venkatachalam. Department of Nutrition, Food and Exercise Sciences, Florida State University, 402 Sandels Bldg., College of Human Sciences, Tallahassee, FL 32306-1493 Numerous studies have reported phaseolin to be resistant to pepsin hydrolysis in vitro. Most of these studies have typically used limited and specific digestion conditions in their experimental protocols such as digestion for limited time, specific phaseolin to pepsin ratios, and fixed HCl (or HCl-NaCl) concentrations. It was therefore not apparent whether the reported resistance of phaseolin to pepsin hydrolysis was due to restricted experimental conditions used or due to inherent resistance of phaseolin towards pepsin. We therefore systematically investigated Great Northern bean (Phaseolus vulgaris L.) phaseolin proteolysis at 370C, varying HCl concentration (10 mM to 1 M), at phaseolin:pepsin ratios ranging from 5:1 to 100:1 (w/w), and incubation times up to 24 h. The results suggest that phaseolin is not resistant to in vitro proteolysis by pepsin. At phaseolin to pepsin ratio 100:1 (w/w) and 50 mM HCl native phaseolin was completely digested in 24 h, while heat denatured phaseolin (30 min at 1000C, boiling water bath) was digested in 1 h under similar conditions. Acid alone, even at 10 mM concentration, caused partial breakdown of native phaseolin in 24 h incubation at 370C. At higher HCl concentrations, phaseolin was degraded substantially and at 1M HCl concentration phaseolin was essentially completely degraded in 24 h when incubated at 370C.
Session 30C, Food Chemistry: Proteins
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