Mechanism of Inhibition of Rice Bran Lipase by Polyphenols: A Case Study with Chlorogenic Acid and Caffeic Acid

Raghavendra Parigi, M.P. and Ramesh, Kumar and Prakash, V. (2007) Mechanism of Inhibition of Rice Bran Lipase by Polyphenols: A Case Study with Chlorogenic Acid and Caffeic Acid. Journal of Food Science, 72 (8). E412-E419.

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Abstract

Rice bran is a byproduct obtained from the rice milling industry, and to arrest lipolysis caused by lipolytic enzyme, rice bran lipase (RBL) was inactivated by inhibitors such as polyphenols. This study describes the inhibition and interaction of enzyme with chlorogenic acid (CGA) and caffeic acid (CA). The inhibition of the enzyme was competitive in nature in both CGA and CA. The inhibition constant K i of the reaction was found to be 1.8 and 1.5 µMfor CGA and CA, respectively. Fluorescence emission measurements indicated a decrease in the fluorescence emission intensity and a red shift in the emissionmaximumas these ligands concentrations are increased, indicating theminorchangesin the tryptophanenvironmentandthe effect ofbindingthat is strongerin the case ofCAcompared to CGA with RBL. Far UV-circular dichroic data suggest that there are no significant changes in the conformation of the enzyme as a result of binding ofCGAor CA. The instability of the enzyme in the presence of these polyphenols has been indicated by decrease in apparent thermal transition temperatures of the enzyme from a control value of 60 ◦C as revealed by thermal denaturation measurements. These results demonstrate that both CGA and CA are inhibitors of RBL and bind to the enzyme through both hydrogen and hydrophobic interaction in bringing about inhibition with minor structural alterations. These inactivation phenomena of polyphenols that act as inhibitors on RBL can be utilized to prevent oxidation of the rice bran oil.

Item Type:	Article
Uncontrolled Keywords:	caffeic acid, chlorogenic acid, conformational stability, hydrophobic interaction, inactivation, polyphenols, rice bran lipase, thermal denaturation temperature
Subjects:	600 Technology > 08 Food technology > 21 Cereals > 01 Rice 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 16 Enzyme Chemistry
Divisions:	Protein Chemistry and Technology
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	09 Aug 2008 06:20
Last Modified:	28 Dec 2011 10:04
URI:	http://ir.cftri.res.in/id/eprint/8670

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