Angiotensin I-converting enzyme inhibitory properties of lentil protein hydrolysates: Determination of the kinetics of inhibition Chockry Barbana, Joyce Irene Boye ⇑ Agriculture and Agri-Food Canada, Food Research and Development Centre, Casavant Blvd. West, St. Hyacinthe, QC, Canada J2S 8E3 article info Article history: Received 14 January 2010 Received in revised form 20 December 2010 Accepted 21 December 2010 Available online 28 December 2010 Keywords: ACE inhibitory activity Bioactivity Lentil protein hydrolysates Lineweaver–Burk abstract ACE inhibitory activity was studied for different hydrolysates obtained from protein concentrates of two lentil varieties by in vitro gastrointestinal simulation, Alcalase/Flavourzyme, papain and bromelain. Pro- tein/peptide profiles studied by electrophoresis and HPLC-SEC showed a rich composition of the hydrol- ysates in small peptides ranging in size from 0.244 to 1.06 kDa. ACE inhibitory activity was measured using the HPLC Hippuryl-His-Leu (HHL) substrate method. Significantly different (P < 0.05) IC 50 values ranging between 0.053 and 0.190 mg/ml were obtained for different hydrolysates. Furthermore, the inhi- bition mechanism investigated using Lineweaver–Burk plots revealed a non-competitive inhibition of ACE with inhibitor constants (K i ) between 0.16 and 0.46 mg/ml. These results demonstrate that hydrol- ysates of lentil proteins obtained by different enzymatic digestions may contain bioactive components. Crown Copyright Ó 2010 Published by Elsevier Ltd. All rights reserved. 1. Introduction Pulses (pea, bean, lentil, chickpea) are the seeds of legumes con- sumed as food in many countries. They are good health-promoting foods, and are nutritionally good sources of carbohydrates (e.g., fi- bre, resistant starch, oligosaccharides), protein, vitamins and min- erals. Additionally, their low fat content supports their consideration for inclusion in a healthy diet regime. Pulses also have low glycemic index resulting in slower digestion. Regular die- tary intake of pulses has been linked with reduced risk of some dis- eases particularly diabetes, cancer and cardiovascular disease (CVD) (Roy, Boye, & Simpson, 2010). Canada is a world leader in pulse production. Total Canadian production of different pulse crops was projected at 5.2 million tonnes (Mt) for 2009 (Agriculture & Agri-Food Canada, 2009). Lentil is an important pulse crop in Canada and is one of the earli- est cultivated crops in the world. Lentil was originally grown in Turkey and other Middle Eastern countries; today, it is produced mainly in India, Turkey, and Canada. Canada and Turkey are amongst the world’s largest lentil exporters. Currently, there are more than 19 registered varieties of lentil in Canada; more than 60% of which belong to the variety Laird (Saskatchewan Pulse Growers, 2000). Lentils are a rich source of proteins and provide a good balance of amino acids. However, large differences in protein content from 24.3% to 30.2% and in the amino acid composition among different varieties of Canadian lentil suggest differences in protein composi- tion (Wang & Daun, 2006), which have been attributed mainly to the combination of genetic and environmental factors. The major proteins found in lentils are albumins and globulins (Gupta & Dhillon, 1993). However, other minor proteins such as prolamins and glutelins are also present. The globulins represent more than 70% of the total proteins and comprise of legumin and vicilin-like proteins. Legumin-like proteins known as 11S globulins are composed of six monomers each having a molecular mass (MM) of about 60 kDa. Each monomer is further sub-divided into acidic (MM approximately 40 kDa) and basic (MM approximately 20 kDa) subunits associated by a disulphide bridge. Vicilin-like proteins or 7S globulins, on the other hand, are composed of three monomers having a MM of 50–80 kDa (Shewry, Jenkins, Beaudoin, & Clare Mills, 2004) with no further sub-divisions. Recent research studies on the potential health benefits of con- suming pulses has spurred interest on their possible protective ef- fects against many chronic diseases, in particular cardiovascular disease (CVD) (Menotti et al., 1999). CVD is a major health risk that provokes more than 29% of total global deaths. It is predicted that in 2010, CVD will be the leading causes of death in developing countries (World Health Organization, 2009). CVD refers to a group of diseases including hypertension, ath- erosclerosis, coronary heart disease, and stroke. Hypertension which is defined as high systolic and diastolic blood pressures is one of the major independent risk factors for CVD. Moreover, ele- vated blood pressure can lead to some of the other forms of CVD cited above (Chen et al., 2009). The renin-angiotensin system is a regulatory mechanism for controlling blood pressure. Renin is an enzyme secreted by the kid- neys which hydrolyses plasma angiotensinogen releasing a 0308-8146/$ - see front matter Crown Copyright Ó 2010 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.12.093 ⇑ Corresponding author. Tel.: +1 450 768 3232; fax: +1 450 773 8461. E-mail address: Joyce.Boye@agr.gc.ca (J.I. Boye). Food Chemistry 127 (2011) 94–101 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem