A review on digestive TAG-lipases of insects

Digestion in insects is a multi-step process to afford nutritional requirements of biological activities. The process starts with nervous stimuli and continues with biochemical activities of digestive enzymes as well as several pumps to digest and absorb the obtained molecules. Carbohydrases, lipases and proteases are the three main digestive enzymes involved in digestion process. Lipases seem to be very important not only for digestive role but also for esteratic activity so that some experts consider lipases as the Class 3 of general esterases. Digestive lipases divided into different groups based on their biological roles namely triacylglycerol lipases, phospholipases and two types of phosphatases. Briefly, triacylglycerol lipases (TAG-lipases) are the hydrolysing enzymes that affect the outer esteric links of triacylglycerols in ingested food. Phospholipases including PLA2 and PLA1 remove phosphatide fatty acids attached to the Position 2 and Position 1. Finally, Alkaline and acid phosphatases are the enzymes that hydrolyse phosphomonoesters under alkaline or acid conditions, respectively. In this review, presence and physiological role of digestive TAG-lipases are explained and their possible importance will be discussed in insect.