Lipase genes expressed in rice bran: LOC_Os11g43510 encodes a novel rice lipase

Rice is a highly consumed staple food all over the world. The economic value of the rice crop can be further increased by producing rice bran oil (RBO) from rice bran which is a by-product of rice milling. However, high utilization of RBO is difficult to achieve as lipases present in rice bran cause decomposition of lipids present in the form of triacyl glycerol (TAG) into free fatty acids (FFA). In this work, we selected and systematically analyzed 125 putative lipase gene sequences derived from Oryza sativa ssp. japonica genome using bioinformatic tools. LOC_Os11g43510 was experimentally demonstrated to be highly expressed in rice bran. Further, molecular modeling and protein docking studies suggested that the protein encoded by LOC_Os11g43510, has high affinity for oleic acid and linoleic acid, common components of TAG in rice. The transcript from LOC_Os11g43510 was cloned and expressed as a secretory protein in Pichia pastoris X-33. SDS-PAGE and zymography showed that expressed protein had lipase activity and was glycosylated. These results are consistent with the hypothesis that LOC_Os11g43510 encodes an active lipase that could be involved in TAG breakdown in rice. This study demonstrates an alternative route to identifying lipases in rice bran.