The proteomic analysis of commercial rice storage proteins in relation to nutrient quality and diabetes mellitus

Abstract

Nutritional quality and diabetes mellitus (DM) are recent concern raised by people when they come across the idea about rice consumption. This concern rose due to the high intake of rice by people around the globe especially Malaysian that consume different types of rice in their daily meal. A part from that, DM also has become one of the serious health problems that claimed to have relationship with the consumption of rice. In this study, the expression level of seed storage protein (SSPs) in three different types of commercial rice; white rice (WR), brown rice (BR) and glutinous rice (GR) have been analysed using proteomic analysis. Through the analysis, among all the three types of rice; BR has significantly the highest concentration of total SSPs, 1.14 ± 0.049 ?g/?l. The relations of the variability in expressed SSPs of the three type of rice with the nutrient quality have been analyzed through SDS-PAGE and 2D-PAGE. There were different protein expressions observed from the protein profile and spots appearance for all the rice types which lead to the variation in the nutrient quality of rice. Five spots were successfully identified which showed different intensity between samples. The identified proteins are two Glutelin proteins, hypothetical protein, 19 kDa globulin precursor and putative prolamin 7. Glutelin and 19 kDa globulin precursor were highly expressed in BR indicated that BR has the highest nutritional quality as glutelin is the major SSPs that contain lysine which is the limiting essential amino acid in cereal. This study also discovered the relation between the SSPs and DM. The prolamin and the albumin of SSPs were found out to have the ability to treat the DM. In this study, prolamin is found out to be the inhibitor protein which has the ability to inhibit the ?- amylase enzyme of Aspergillus oryzae. Among the three types of rice, BR have significantly high content of inhibitor protein (0.030 ± 0.002 ?g/?l) compared to WR (0.005 ± 0.001?g/?l) and GR (0.006 ± 0.001 ?g/?l). BR also showed the highest inhibition of 56.12 % compared to WR and GR with percentage of – 61.22 and – 177.35 % respectively. As BR possessed the high percentage of inhibition compared to WR (6.196 ± 0.196 mg/ml) and GR (8.353 ± 0.339 mg/ml), it produced the lowest formation of maltose of 1.69 ± 1.092 mg/ml. Therefore, BR possessed the best characteristic for daily diet for consumers especially for the patients with Diabetes Mellitus compared to WR and GR.